- Generation of alkylidene carbenes from α,β-epoxy-N-aziridinyl imines. A new route to cyclopentenols
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Thermal reaction of α,β-epoxy-N-aziridinyl imines in refluxing toluene would initially generate the reactive alkylidene carbenes which underwent intramolecular carbon-hydrogen insertion reactions to afford cyclopentenols.
- Kim, Sunggak,Cho, Chang Mook
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- Catalytic studies of cyclometalated gold(III) complexes and their related UiO-67 MOF
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Cyclometalated gold(III) complexes Au(L)(OAcF)2 (L = phenylpyridine dicarboxylic diester (ppyde) or phenylpyridine dicarboxylic acid (ppydc)) have been prepared reacting Au(OAc)3 with corresponding phenyl pyridines (ppyde or ppydc) in trifluoroacetic acid (HOAcF) under microwave heating. Further treatment of Au(L)(OAcF)2 with aqua regia resulted in dichloro complexes Au(L)Cl2. Au-functionalized UiO-67 MOF has been synthesized by exchanging linkers of UiO-67 with Au(ppydc)Cl2, furnishing the MOF with (N^C)-cyclometalated Au(III) centers. The catalytic activities of the molecular cyclometalated complexes and the Au-incorporated MOF were studied in gold-catalyzed propargyl ester cyclopropanations. Almost all complexes and the MOF showed catalytic activity to the cyclopropanation product (up to 97% conversion), with a preference for the trans diastereoisomer (up to 14:86 d.r.). The recyclability of the most active molecular complex has also been investigated.
- ?ien-?degaard, Sigurd,Fiksdahl, Anne,Kaur, Gurpreet,Levchenko, Volodymyr A.,Siah, Huey-San Melanie,Tilset, Mats
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- A chemoselective deprotection of trimethylsilyl acetylenes catalyzed by silver salts
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Trimethylsilyl acetylenes can be selectively deprotected in the presence of a catalytic amount of silver salts. AgNO3 and AgOTf proved to be the most effective catalyst in a mixture of methanol, water and dichloromethane. Other functional groups, and especially silyl ethers, are not affected in these conditions.
- Orsini, Alban,Vitérisi, Aurélien,Bodlenner, Anne,Weibel, Jean-Marc,Pale, Patrick
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- Aromatic Rings and Aromatic Rods: Nonplanar Character of an Indeno-dehydro[14]annulene
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Since the concept of aromaticity has been proposed to be generalizable to acetylenic rods ('linear ring' of [2]annulene), p-diisopropyl-tetraphenyl-carbo-benzene (C48H34) and an indenone-fused isopropyl-triphenyloctadehydro[14]annulene (C42H26O) can be regarded as based on heptacyclic aromatic cores. The formation and X-ray crystal structures of both products are described. The latter has been obtained as a reductive rearrangement product of a transient isopropyl-pentaoxy[5]pericyclyne devised as a putative precursor of a carbo-fulvene target. A mechanism accounting for this peculiar transformation is proposed. Deviation from global planarity is measured by a 6° angle between the mean plane of the indenone bicycle and that of 13 atoms of the [14]annulenic macrocycle, forming dihedral angles with the local plane of the isopropyl-substituted sp2 vertex of 16° and 15°, respectively. The magnetic aromaticity of the carbo-benzene and indeno-octadehydro[14]annulene products is evaluated by NICS calculations.
- Cocq, Kévin,Saffon-Merceron, Nathalie,Poater, Albert,Maraval, Valérie,Chauvin, Remi
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- Enantio- And Diastereodivergent Construction of 1,3-Nonadjacent Stereocenters Bearing Axial and Central Chirality through Synergistic Pd/Cu Catalysis
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In contrast to the widely explored methods for the asymmetric synthesis of molecules bearing a single stereocenter or adjacent stereocenters, the concurrent construction of 1,3-stereogenic centers in an enantio- and diastereoselective manner remains a challenge, especially in acyclic systems. Herein, we report an enantio- and diastereodivergent construction of 1,3-nonadjacent stereocenters bearing allenyl axial and central chirality through synergistic Pd/Cu-catalyzed dynamic kinetic asymmetric allenylation with racemic allenylic esters. The protocol is suitable for a wide range of substrates including the challenging allenylic esters with less sterically bulky substituents and provided chiral allenylic products bearing 1,3-nonadjacent stereocenters with high levels of enantio- and diastereoselectivities (up to >20:1 dr and >99% ee). Furthermore, several representative transformations involving axial-to-central chirality transfer were conducted, affording useful structural motifs containing nonadjacent stereocenters in a diastereodivergent manner.
- Huo, Xiaohong,Ma, Shengming,Xiao, Junzhe,Zhang, Jiacheng,Zhang, Wanbin,Zhao, Ling
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supporting information
p. 12622 - 12632
(2021/08/31)
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- Multisubstituted pyrazole synthesis via [3?+?2] cycloaddition/rearrangement/N[sbnd]H insertion cascade reaction of α-diazoesters and ynones
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The cascade reactions of alkyl α-diazoesters and ynones using Al(OTf)3 as the catalyst are described. A series of 4-substituted pyrazoles were obtained via [3 + 2] cycloaddition, 1,5-ester shift, 1,3-H shift, and N[sbnd]H insertion process. Deuterium labelling experiments, kinetic studies and control experiments were carried out for the rationalization of the mechanism.
- Feng, Xiaoming,Liu, Xiaohua,Zeng, Zi,Zhao, Peng
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p. 132 - 135
(2020/12/21)
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- Mono-Gold(I)-Catalyzed Enantioselective Intermolecular Reaction of Ynones with Styrenes: Tandem Diels–Alder and Ene Sequence
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Gold-catalyzed intermolecular reaction leading to dihydronaphthalene derivatives in one pot from two equivalents of ynones with respect to styrene is uncovered. The [4+2] Diels–Alder cycloaddition of ynones and styrenes is catalyzed by a mono-gold(I) complex and the conjugated acid to provide an unstable 3,8a-dihydronaphthalene to subsequently undergo an intermolecular ene-type reaction with the π-activated ynone to afford multi-component coupling dihydronaphthalene products. Linear relationships between chiral ligand-gold complexes and chiral dihydronaphthalene products proves mono-gold catalysis that triggers an asymmetric tandem Diels–Alder and ene reaction sequence.
- Nanko, Masaki,Inaba, Yuya,Sekine, Keisuke,Mikami, Koichi
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- Allenylidene Induced 1,2-Metalate Rearrangement of Indole-Boronates: Diastereoselective Access to Highly Substituted Indolines
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A process to achieve 1,2-metalate rearrangements of indole boronate as a way to access substituted indolines in high diastereoselectivities is presented. The reaction involves the generation of a Cu–allenylidene, which is sufficiently electrophilic to induce the 1,2-metalate rearrangement. The scope of the reaction is evaluated as well as further transformations of the product.
- Simlandy, Amit Kumar,Brown, M. Kevin
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supporting information
p. 12366 - 12370
(2021/05/03)
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- Gold-Catalyzed Iminations of Terminal Propargyl Alcohols with Anthranils with Atypical Chemoselectivity for C(1)-Additions and 1,2-Carbon Migration
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This work reports gold-catalyzed iminations of terminal propargyl alcohols with anthranils or isoxazoles to yield E-configured α-amino-2-en-1-ones and -1-als with complete chemoselectivity. These catalytic iminations occur exclusively with C(1)-nucleophilic additions on terminal alkynes, in contrast to a typical C(2)-route. For 3,3-dialkylprop-1-yn-3-ols, a methyl substituent is superior to long alkyl chains as the 1,2-migration groups toward α-imino gold carbenes. For secondary prop-1-yn-3-ols, phenyl, vinyl, and cyclopropyl substituents are better than hydrogen as the migrating groups, obviating typical gold carbene reactions. DFT calculations have been performed to rationalize the observed C(1)-regioselectivity and the preferable cyclopropyl migration based on gold carbene pathways.
- Skaria, Manisha,More, Sayaji Arjun,Kuo, Tung-Chun,Cheng, Mu-Jeng,Liu, Rai-Shung
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p. 3600 - 3608
(2020/03/04)
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- Laccase-mediated Oxidations of Propargylic Alcohols. Application in the Deracemization of 1-arylprop-2-yn-1-ols in Combination with Alcohol Dehydrogenases
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The catalytic system composed by the laccase from Trametes versicolor and the oxy-radical TEMPO has been successfully applied in the sustainable oxidation of fourteen propargylic alcohols. The corresponding propargylic ketones were obtained in most cases in quantitative conversions (87–>99 % yield), demonstrating the efficiency of the chemoenzymatic methodology in comparison with traditional chemical oxidants, which usually lead to problems associated with the formation of by-products. Also, the stereoselective reduction of propargylic ketones was studied using alcohol dehydrogenases such as the one from Ralstonia species overexpressed in E. coli or the commercially available evo-1.1.200, allowing the access to both alcohol enantiomers mostly with complete conversions and variable selectivities depending on the aromatic pattern substitution (97–>99 % ee). To demonstrate the compatibility of the laccase-mediated oxidation and the alcohol dehydrogenase-catalyzed bioreduction, a deracemization strategy starting from the racemic compounds was developed through a sequential one-pot two-step process, obtaining a selection of (S)- or (R)-1-arylprop-2-yn-1-ols with excellent yields (>98 %) and selectivities (>98 % ee) depending on the alcohol dehydrogenase employed.
- González-Granda, Sergio,Méndez-Sánchez, Daniel,Lavandera, Iván,Gotor-Fernández, Vicente
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p. 520 - 527
(2019/11/16)
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- Cracking under internal pressure: Photodynamic behavior of vinyl azide crystals through N2release
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When exposed to UV light, single crystals of the vinyl azides 3- azido-1-phenylpropenone (1a), 3-azido-1-(4-methoxyphenyl)propenone (1b), and 3-azido-1-(4-chlorophenyl)propenone (1c) exhibit dramatic mechanical effects by cracking or bending with the release of N2. Mechanistic studies using laser flash photolysis, supported by quantum mechanical calculations, show that each of the vinyl azides degrades through a vinylnitrene intermediate. However, despite having very similar crystal packing motifs, the three compounds exhibit distinct photomechanical responses in bulk crystals. While the crystals of 1a delaminate and release gaseous N2 indiscriminately under paraffin oil, the crystals of 1b and 1c visibly expand, bend, and fracture, mainly along specific crystallographic faces, before releasing N2. The photochemical analysis suggests that the observed expansion is due to internal pressure exerted by the gaseous product in the crystal lattices of these materials. Lattice energy calculations, supported by nanoindentation experiments, show significant differences in the respective lattice energies. The calculations identify critical features in the crystal structures of 1b and 1c where elastic energy accumulates during gas release, which correspond to the direction of the observed cracks. This study highlights the hitherto untapped potential of photochemical gas release to elicit a photomechanical response and motility of photoreactive molecular crystals.
- Shields, Dylan J.,Karothu, Durga Prasad,Sambath, Karthik,Ranaweera, Ranaweera A. A. Upul,Schramm, Stefan,Duncan, Alexander,Duncan, Benjamin,Krause, Jeanette A.,Gudmundsdottir, Anna D.,Naumov, Pan?e
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p. 18565 - 18575
(2020/12/01)
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- An Enantioconvergent Benzylic Hydroxylation Using a Chiral Aryl Iodide in a Dual Activation Mode
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The application of a triazole-substituted chiral iodoarene in a direct enantioselective hydroxylation of alkyl arenes is reported. This method allows the rapid synthesis of chiral benzyl alcohols in high yields and stereocontrol, despite its nontemplated nature. In a cascade activation consisting of an initial irradiation-induced radical C-H-bromination and a consecutive enantioconvergent hydroxylation, the iodoarene catalyst has a dual role. It initiates the radical bromination in its oxidized state through an in-situ-formed bromoiodane and in the second, Cu-catalyzed step, it acts as a chiral ligand. This work demonstrates the ability of a chiral aryl iodide catalyst acting both as an oxidant and as a chiral ligand in a highly enantioselective C-H-activating transformation. Furthermore, this concept presents an enantioconvergent hydroxylation with high selectivity using a synthetic catalyst.
- Abazid, Ayham H.,Clamor, Nils,Nachtsheim, Boris J.
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p. 8042 - 8048
(2020/09/21)
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- Covalent Adaptable Networks with Tunable Exchange Rates Based on Reversible Thiol–yne Cross-Linking
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The design of covalent adaptable networks (CANs) relies on the ability to trigger the rearrangement of bonds within a polymer network. Simple activated alkynes are now used as versatile reversible cross-linkers for thiols. The click-like thiol–yne cross-linking reaction readily enables network synthesis from polythiols through a double Michael addition with a reversible and tunable second addition step. The resulting thioacetal cross-linking moieties are robust but dynamic linkages. A series of different activated alkynes have been synthesized and systematically probed for their ability to produce dynamic thioacetal linkages, both in kinetic studies of small molecule models, as well as in stress relaxation and creep measurements on thiol–yne-based CANs. The results are further rationalized by DFT calculations, showing that the bond exchange rates can be significantly influenced by the choice of the activated alkyne cross-linker.
- Du Prez, Filip E.,Guerre, Marc,Maes, Diederick,Unal, Kamil,Van Herck, Niels,Winne, Johan M.
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supporting information
p. 3609 - 3617
(2020/02/04)
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- A sustainable access to ynones through laccase/TEMPO-catalyzed metal- and halogen-free aerobic oxidation of propargylic alcohols in aqueous medium
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Tuning laccase/TEMPO-catalyzed aerobic oxidation of secondary propargylic alcohols in aqueous media was accomplished in order to efficiently synthesize ynones. This study led to the formulation of an effective and sustainable catalytic method for the preparation of mono- and bis-substituted ynones compared with traditional oxidative methods.
- Silva, Alana B.V.,Silva, Emmanuel D.,dos Santos, Alcindo A.,Princival, Jefferson L.
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- Synthesis of (Z)-alkene-containing linear conjugated dienyl homoallylic alcohols by a palladium-catalyzed three-component reaction
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A synthesis of (Z)-alkene-containing linear conjugated dienyl homoallylic alcohols by using a palladium-catalyzed three-component reaction has been developed. This method shows good functional-group compatibility and generality, with high diastereoselectivity. Additionally, in many cases, the present method controls the alkene stereochemistry of the newly formed C-C bond and overcomes the inherent preference for (E)-alkene formation, giving (Z, E)- and (Z, Z)-products.
- Horino, Yoshikazu,Sakamoto, Juri,Murakami, Miki,Sugata, Miki
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supporting information
p. 1323 - 1327
(2020/08/21)
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- Enantioselective Hydroboration of Ketones Catalyzed by Rare-Earth Metal Complexes Containing Trost Ligands
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Four chiral dinuclear rare-earth metal complexes [REL1]2 (RE = Y(1), Eu(2), Nd(3), La (4)) stabilized by Trost proligand H3L1 (H3L1 = (S,S)-2,6-bis[2-(hydroxydiphenylmethyl)pyrrolidin-1-ylmethyl]-4-methylphenol) were first prepared, and all were characterized by X-ray diffraction. Complex 4 was employed as the catalyst for enantioselective hydroboration reaction of substituted ketones, and the corresponding secondary alcohols with excellent yields and high ee values were obtained using reductant HBpin. The same result was also achieved using the combination of lanthanium amides La[N(SiMe3)2]3 with Trost proligand H3L1 in a 1:1 molar ratio. The experimental findings and DFT calculation revealed the possible mechanism of the enantioselective hydroboration reaction and defined the origin of the enantioselectivity in the current system.
- Lu, Chengrong,Sun, Yuli,Xue, Mingqiang,Zhao, Bei
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p. 10504 - 10513
(2020/09/23)
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- Metal-free synthesis of activated ynesulfonamides and tertiary enesulfonamides
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An operationally simple synthesis of activated ynesulfonamides and enesulfonamides is described. Ynesulfonamides can be obtained through reaction of sulfonylamides with activated bromoalkynes and Triton B in a short time at room temperature. Likewise, terminal alkynes react with sulfonylamides to provide enesulfonamides. Z/E enesulfonamides can be transformed exclusively into E enesulfonamides.
- Andna, Lucile,Miesch, Laurence
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p. 5688 - 5692
(2019/06/19)
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- Regioselectivity Switch in Palladium-Catalyzed Allenylic Cycloadditions of Allenic Esters: [4+1] or [4+3] Cycloaddition/Cross-Coupling
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The first Pd-catalyzed asymmetric allenylic [4+1] cycloaddition was successfully developed. Alternatively, tuning the Pd catalyst switched the reactivity toward an unprecedented [4+3] cycloaddition/cross-coupling. Ligands play a vital role in controlling the reaction pathway, allowing highly selective access to different products from identical substrates. Biological evaluation of the obtained compounds led to the discovery of new antitumor targets. A possible mechanism is proposed, suggesting two interesting catalytic cycles for the cycloaddition with palladium-butadienyls. This study also demonstrated the potential and utility of allenic esters as 1,4-biselectrophiles and C4 synthons for participating in cycloaddition reactions.
- Li, Long,Luo, Pengfei,Deng, Yuhua,Shao, Zhihui
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supporting information
p. 4710 - 4713
(2019/03/08)
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- Hafnium trifluoromethanesulfonate catalyzed silyl ether protecting group removing method
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The invention provides a hafnium trifluoromethanesulfonate catalyzed silyl ether protecting group removing method. Various silyl ether protecting groups of nearly 50 kinds of substrates can be efficiently removed in 0.5-16 hours at room temperature by taking 0.02mol%-0.3mol% hafnium trifluoromethanesulfonate as a catalyst, a silyl ether protected hydroxyl compound as a substrate and conventional AR methanol as a solvent. 42 kinds of silyl ether protecting group removing products can be obtained at high yield by performing conventional slica column chromatography purification on a crude product. By regulating the use amount of the catalyst, the Hf(OTf)4 catalyst can realize regioselective removal of 1-degree, 2-degree and 3-degree alkyl TBS and aryl TBS protective groups. Moreover, in a proper equivalent scope, the Hf(OTf)4 catalyst can also realize 1) chemoselective removal of different kinds of silica-based protective groups; and 2) chemoselective removal of 1-degree TBS protective groups under the condition of not affecting a majority of common hydroxyl protective groups.
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Paragraph 0009; 0014
(2019/01/21)
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- Coupling-Isomerization-Cycloisomerization Reaction (CICIR) – An Unexpected and Efficient Domino Approach to Luminescent 2-(Hydroxymethylene)indenones
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A Pd/Cu-catalyzed base mediated domino process of ortho-halo (hetero)aryl carboxaldehydes and propargyl alcohols unexpectedly furnish 2-(hydroxymethylene)indenones in good to excellent yield as a result of a coupling-isomerization-cycloisomerization reaction (CICIR). In addition, the title compounds constitute an interesting class of luminophores with tunable emission solvatochromicity.
- Ghazvini, Helya Janatian,Armaghan, Mahsa,Janiak, Christoph,Balalaie, Saeed,Müller, Thomas J. J.
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supporting information
p. 7058 - 7062
(2019/11/11)
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- Regioselective dehydroxytrifluoromethylthiolation of allylic and propargylic alcohols with AgSCF3
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The reaction of easily available Morita–Baylis–Hillman (MBH) alcohols with AgSCF3 in the presence of n-Bu4NI and KI affords primary allylic SCF3 products in high yields and excellent regioselectivities. This regioselective dehydroxytrifluoromethylthiolation protocol could also be extended to propargylic alcohols for the preparation of the primary propargylic SCF3 products.
- Liu, Yin-Li,Xu, Xiu-Hua,Qing, Feng-Ling
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supporting information
p. 953 - 956
(2019/03/07)
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- Phosphonium-Ring-Fused Bicyclic Metallafuran Complexes of Ruthenium and Osmium
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Metallafuran complexes with a fused five-membered phosphonium ring were synthesized from reactions between terminal ynones HC≡C(C=O)R and cis-[Ru/Os(dppm)2Cl2] (dppm=1,1-bis(diphenylphosphino)methane). A metal–vinylidene-involving pathway was found to be an energetically feasible formation mechanism for these complexes. These phosphonium-containing metallafurans, like many phosphonium-functionalized drugs, have the ability to induce mitochondrial dysfunction. They also exhibit stronger cytotoxicity against several human cancer cell lines in comparison with their metal precursors and the classic anticancer drug cisplatin. Overall, this work provides structural and mechanistic insights for the rational design of functional metallacycles via activation of alkynes by RuII and OsII centers.
- Yeung, Chi-Fung,Chung, Lai-Hon,Ng, Sze-Wing,Shek, Hau-Lam,Tse, Sheung-Ying,Chan, Siu-Chung,Tse, Man-Kit,Yiu, Shek-Man,Wong, Chun-Yuen
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supporting information
p. 9159 - 9163
(2019/06/10)
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- Palladium-catalyzed [3+2] annulation of allenyl carbinol acetates with C,N-cyclic azomethine imines
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In this paper, a palladium-catalyzed [3+2] annulation of allenyl carbinol acetates with azomethine imines has successfully been developed under mild reaction conditions, affording biologically interesting tetrahydropyrazoloisoquinoline derivatives in high to excellent yields and with excellent stereoselectivity. The reaction follows a tandem [3+2] cycloaddition/allylation/elimination of AcOH pathway. Allenyl carbinol acetates also reacted well with in situ generated azomethine imine under cocatalysis of Ag(i)/Pd(0) catalysts in a similar reaction pathway.
- Mao, Biming,Zhang, Junya,Xu, Yi,Yan, Zhengyang,Wang, Wei,Wu, Yongjun,Sun, Changqing,Zheng, Bing,Guo, Hongchao
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supporting information
p. 12841 - 12844
(2019/11/05)
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- Flavylium Salts: A Blooming Core for Bioinspired Ionic Liquid Crystals
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Thermotropic ionic liquid crystals based on the flavylium scaffold have been synthesized and studied for their structure-properties relationship for the first time. The mesogens were probed by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction (XRD). Low numbers of alkoxy side chains resulted in smectic (SmA) and lamello-columnar (LamCol) phases, whereas higher substituted flavylium salts showed Colro as well as ordered and disordered columnar (Colho, Colhd) mesophases. Mesophase width ranged from 13 K to 220 K, giving access to room temperature liquid crystals. The optical properties of the synthesized compounds were probed towards absorption and emission properties. Strong absorption with maxima between 444 and 507 nm was observed, and some chromophores were highly emissive with quantum yields up to 99 %. Ultimately, mesogenic and dye properties were examined by temperature-dependent emissive experiments in the solid state.
- Forschner, Robert,Knelles, Jakob,Bader, Korinna,Müller, Carsten,Frey, Wolfgang,K?hn, Andreas,Molard, Yann,Giesselmann, Frank,Laschat, Sabine
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supporting information
p. 12966 - 12980
(2019/11/05)
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- Hafnium Triflate as a Highly Potent Catalyst for Regio- and Chemoselective Deprotection of Silyl Ethers
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As a Group IVB transition metal Lewis acid, hafnium triflate [Hf(OTf) 4 ] exhibited exceptionally high potency in desilylations. Since the amounts of Hf(OTf) 4 required for the deprotection of 1°, 2°, 3° alkyl and aryl tert -butyldimethylsilyl (TBS) ethers are significantly different, ranging from 0.05 mol% to 3 mol%, regioselective deprotection of TBS could be easily implemented. Moreover, chemoselective cleavage of different silyl ethers or removal of TBS in the presence of most hydroxyl protecting groups was also accomplished. NMR analyses of silyl products from TBS deprotection indicated that Hf(OTf) 4 -catalyzed desilylation may proceed via different mechanisms, depending on the solvent used.
- Zheng, Xiu-An,Kong, Rui,Huang, Hua-Shan,Wei, Jing-Ying,Chen, Ji-Zong,Gong, Shan-Shan,Sun, Qi
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supporting information
p. 944 - 953
(2019/02/10)
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- Lipase/Oxovanadium Co-Catalyzed Dynamic Kinetic Resolution of Propargyl Alcohols: Competition between Racemization and Rearrangement
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Quantitative conversion of racemic propargyl alcohols into optically active propargyl esters with up to 99% ee has been achieved by lipase/oxovanadium co-catalyzed dynamic kinetic resolution, which combines the lipase-catalyzed enantioselective esterification of the racemic substrates and the in situ racemization of the remaining enantiomers. The success is owed to our discovery of a magic solvent, (trifluoromethyl)benzene, that accelerated the racemization while sufficiently suppressing the common oxovanadium-catalyzed rearrangement of propargyl alcohols to irreversibly produce enals.
- Kawanishi, Shinji,Oki, Shinya,Kundu, Dhiman,Akai, Shuji
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supporting information
p. 2978 - 2982
(2019/03/26)
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- Trialkylborane-Mediated Propargylation of Aldehydes Using γ-Stannylated Propargyl Acetates
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A transition-metal-free three-component process that combines aldehydes, 3-(tributylstannyl)propargyl acetates formed in situ from readily available propargyl acetates, and trialkylboranes provides access to a range of 1,2,4-trisubstituted homopropargylic alcohols. The addition of diisopropylamine plays a crucial role in the selective formation of homopropargylic alcohols. Importantly, this methodology can be extended to a single-flask reaction sequence starting from propargyl acetates.
- Horino, Yoshikazu,Murakami, Miki,Ishibashi, Mayo,Lee, Jun Hee,Watanabe, Airi,Matsumoto, Rio,Abe, Hitoshi
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supporting information
p. 9564 - 9568
(2019/12/24)
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- Trialkylborane-Mediated Multicomponent Reaction for the Diastereoselective Synthesis of Anti-δ,δ-Disubstituted Homoallylic Alcohols
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The trialkylborane/O2-mediated reaction of propargyl acetates having a tributylstannyl group at an alkyne terminus with aldehydes in a THF-H2O solvent system gave anti-δ,δ-disubstituted homoallylic alcohols with good to high diastereoselectivity. Intriguingly, two alkyl groups derived from trialkylborane were embedded into the reaction product. The trialkylborane plays a key role not only as a radical initiator but also as a source of alkyl radicals.
- Horino, Yoshikazu,Murakami, Miki,Aimono, Ataru,Lee, Jun Hee,Abe, Hitoshi
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supporting information
p. 476 - 480
(2019/01/14)
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- 1,1-Diphosphines and divinylphosphines via base catalyzed hydrophosphination
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A catalytic hydrophosphination route to 1,1-diphosphines is yet to be reported: these narrow bite angle pro-ligands have been used to great effect as ligands in homogeneous catalysis. We herein demonstrate that terminal alkynes readily undergo double hydrophosphination with HPPh2 and catalytic potassium hexamethyldisilazane (KHMDS) to generate 1,1-diphosphines. A change to H2PPh leads to the formation of P,P-divinyl phosphines.
- Coles,Mahon,Webster
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supporting information
p. 10443 - 10446
(2018/09/21)
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- Gold(I)-Catalyzed Tandem Cycloisomerization and Fluorination of 1,3(4)-Enyne Esters with NFSI: One-Pot Assembly of 5-Fluoro- Cyclopentenones
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An efficient synthetic approach for the synthesis of 5-fluoro-cyclopentenones containing a fluorine-substituted carbon stereocenter that relies on gold(I)-catalyzed cycloisomerization and fluorination sequence of 1,3(4)-enyne esters with N-fluorbenzensulfonimide (NFSI) is described. This tandem transformation exhibited a broad substrate scope and excellent functional group compatibility, providing a novel protocol for rapid assembly 5-fluoro-cyclopentenones in good to excellent yields under mild reaction conditions. The mechanistic studies revealed that the transformation involves a gold-catalyzed cycloisomerization and electrophilic fluorination cascade to give the 5-fluoro-cyclopentenones. (Figure presented.).
- Chen, Xianxiao,Zhou, Yuanyuan,Hong, Mei,Ling, Yuan,Yin, Dongliang,Wang, Shifa,Zhang, Xiaoxiang,Rao, Weidong
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p. 3700 - 3708
(2018/09/12)
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- One-pot synthesis of polyfunctionalized quinolines: Via a copper-catalyzed tandem cyclization
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An efficient one-pot approach for the synthesis of polyfunctionalized quinolines was developed via a sequence of copper-catalyzed coupling reaction/propargyl-allenyl isomerization/aza-electrocyclization. Easily available starting materials, mild conditions, and a wide substrate scope make this approach potentially useful.
- Chen, Dianpeng,Sun, Xuejun,Shan, Yingying,You, Jinmao
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supporting information
p. 7657 - 7662
(2018/11/02)
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- Cascade and Effective Syntheses of Functionalized Tellurophenes
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A one-pot and transition-metal-catalyst-free synthetic strategy to construct functionalized tellurophenes has been developed. Substituted 1,1-dibromo-1-en-3-ynes are smoothly converted to tellurophenes with telluride salts in high yield via a series of cascade reactions through reductive debromination, hydrotelluration, nucleophilic cyclization, and aromatization. Close inspection of the results clearly showed that the reactivity of in situ prepared telluride salts are significantly influenced by the polarity of the solvent system and the electronic nature of the substituent on the enyne substrate. This method reports the first direct synthesis of 3-aryltellurophenes in high yields at room temperature. This novel reaction strategy is also found to be a promising synthetic method for multisubstituted tellurophenes and selenophenes.
- Karapala, Vamsi Krishna,Shih, Hong-Pin,Han, Chien-Chung
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supporting information
p. 1550 - 1554
(2018/03/23)
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- Bifunctional Ligand Enables Efficient Gold-Catalyzed Hydroalkenylation of Propargylic Alcohol
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Using the previously designed biphenyl-2-ylphosphine ligand, featuring a remote tertiary amino group, the first gold-catalyzed intermolecular hydroalkenylation of alkynes has been developed. Synthetically valuable conjugated dienyl alcohols are formed in moderate to good yields. A range of alkenyltrifluoroborates are allowed as the alkenyl donor, and no erosion of alkene geometry and/or the propargylic configuration are detected. DFT calculations confirm the critical role of the remote basic group in the ligand as a general-base catalyst for promoting this novel gold catalysis with good efficiency.
- Liao, Shengrong,Porta, Alessio,Cheng, Xinpeng,Ma, Xu,Zanoni, Giuseppe,Zhang, Liming
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supporting information
p. 8250 - 8254
(2018/06/29)
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- A Vinyl-Boronate Ester-Based Persulfide Donor Controllable by Hydrogen Peroxide, a Reactive Oxygen Species (ROS)
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A vinyl boronate ester-based persulfidating agent that is selectively activated by hydrogen peroxide, which is a reactive oxygen species (ROS), and efficiently generated a persulfide by a hitherto unexplored 1,4-O,S-relay mechanism is reported. This donor was found to protect cells from cytotoxicity induced by oxidants, and the major byproduct is cinnamaldehyde, which is widely used in the food industry as an additive.
- Bora, Prerona,Chauhan, Preeti,Manna, Suman,Chakrapani, Harinath
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supporting information
p. 7916 - 7920
(2019/01/04)
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- Gem-Digold Acetylide Complexes for Catalytic Intermolecular [4 + 2] Cycloaddition: Having Two Gold Centers Is Better for Asymmetric Catalysis
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Gold(I)-catalyzed highly enantioselective intermolecular [4 + 2] cycloaddition is shown with ynones and cyclohexadiene. Various bicyclo[2.2.2]octadiene derivatives are produced in high yields (up to 99%) with good enantioselectivity (up to 96% ee). Key to the success is generation of the gem-digold terminal alkyne as a catalytic on-cycle species. As proof of the gem-digold catalysis, a positive nonlinear effect is clarified between the ee's of the ligand and the cycloadduct.
- Nanko, Masaki,Shibuya, Satoru,Inaba, Yuya,Ono, Soichiro,Ito, Shigekazu,Mikami, Koichi
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supporting information
p. 7353 - 7357
(2018/10/15)
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- Acylative Kinetic Resolution of Alcohols Using a Recyclable Polymer-Supported Isothiourea Catalyst in Batch and Flow
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A polystyrene-supported isothiourea catalyst, based on the homogeneous catalyst HyperBTM, has been prepared and used for the acylative kinetic resolution of secondary alcohols. A wide range of alcohols, including benzylic, allylic, and propargylic alcohols, cycloalkanol derivatives, and a 1,2-diol, has been resolved using either propionic or isobutyric anhydride with good to excellent selectivity factors obtained (28 examples, s values up to 600). The catalyst can be recovered and reused by a simple filtration and washing sequence, with no special precautions needed. The recyclability of the catalyst was demonstrated (15 cycles) with no significant loss in either activity or selectivity. The recyclable catalyst was also used for the sequential resolution of 10 different alcohols using different anhydrides with no cross-contamination between cycles. Finally, successful application in a continuous flow process demonstrated the first example of an immobilized Lewis base catalyst used for the kinetic resolution of alcohols in flow.
- Neyyappadath, Rifahath Mon,Chisholm, Ross,Greenhalgh, Mark D.,Rodríguez-Escrich, Carles,Pericàs, Miquel A.,H?hner, Georg,Smith, Andrew D.
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p. 1067 - 1075
(2018/02/14)
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- Direct spirocyclization from keto-sulfonamides: An approach to azaspiro compounds
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Spontaneous spirocyclization of keto-sulfonamides via ynamides through a one-pot process is presented. Push-pull ynamides were obtained through Michael addition/elimination without Cu. The obtained azaspiro compounds are building blocks for indole alkaloids. Theoretical studies provide insights into the mechanism of the formal Conia-ene reaction.
- Beltran, Frédéric,Fabre, Indira,Ciofini, Ilaria,Miesch, Laurence
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p. 5042 - 5045
(2017/11/06)
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- An Unexpected Domino Reaction of β-Keto Sulfones with Acetylene Ketones Promoted by Base: Facile Synthesis of 3(2H)-Furanones and Sulfonylbenzenes
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An unexpected domino reaction of β-keto sulfones with acetylene ketones has been developed. The domino reaction of β-keto sulfones with diynones proceeded smoothly in the presence of 30 mol% K2CO3 without other additives, and afforded the novel 3(2H)-furanone derivatives. On replacing the diynones with terminal alkyne ketones, the reaction regioselectivity was changed and sulfonylbenzenes were obtained via benzannulation in good yields. (Figure presented.).
- Tong, Wei,Li, Qian-Yu,Xu, Yan-Li,Wang, Heng-Shan,Chen, Yan-Yan,Pan, Ying-Ming
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p. 4025 - 4035
(2017/11/21)
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- Gold-Catalyzed Dehydrogenative Cycloisomerization of 1,4-Enyne Esters to 3,5-Disubstituted Phenol Derivatives
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A method to prepare synthetically important 3,5-disubstituted phenol derivatives that relies on the sequential gold(I)-catalyzed dehydrogenative cycloisomerization of 1,4-enyne esters in the presence of 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) or N-fluorobenzenesulfonimide (NFSI) is described. The synthetic versatility of the methodology was exemplified by a gram-scale reaction of one example, the ease to realize subsequent functional transformations of an adduct, and the application of the method to the synthesis of the bioactive molecule LUF5771. (Figure presented.).
- Chen, Cuili,Chen, Xianxiao,Zhang, Xiaoxiang,Wang, Shifa,Rao, Weidong,Chan, Philip Wai Hong
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p. 4359 - 4368
(2017/12/26)
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- Ni-Catalyzed regio- and stereoselective addition of arylboronic acids to terminal alkynes with a directing group tether
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Addition of arylboronic acids to directing group tethered acetylenes in a regio and stereoselective manner using an inexpensive catalytic system is achieved for the first time to access highly sought after allyl/homoallyl alcohol/amine units. The apparent vinylnickel intermediate was successfully trapped by the Michael electrophiles to get defined tri- and tetra-substituted olefins. An interesting selectivity switch was observed with internal alkynes.
- Hari Babu, Madala,Ranjith Kumar, Gadi,Kant, Ruchir,Sridhar Reddy, Maddi
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supporting information
p. 3894 - 3897
(2017/04/04)
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- Synthesis of Vinyl-, Allyl-, and 2-Boryl Allylboronates via a Highly Selective Copper-Catalyzed Borylation of Propargylic Alcohols
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An efficient methodology for the synthesis of vinyl-, allyl-, and (E)-2-boryl allylboronates from propargylic alcohols via Cu-catalyzed borylation under mild conditions is reported. In the presence of commercially available Cu(OAc)2 or Cu(acac)2 and Xantphos, the reaction affords the desired products in up to 92% yield with a broad substrate scope (43 examples). Isolation of an allenyl boronate as the reaction intermediate suggests that an insertion-elimination-type reaction, followed by borylcupration, is involved in the borylation of propargylic alcohols.
- Mao, Lujia,Bertermann, Rüdiger,Emmert, Katharina,Szabó, Kálmán J.,Marder, Todd B.
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supporting information
p. 6586 - 6589
(2017/12/26)
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- Well-Defined Chiral Gold(III) Complex Catalyzed Direct Enantioconvergent Kinetic Resolution of 1,5-Enynes
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The development of a gold(III) catalyzed direct enantioconvergent 1,5-enyne cycloisomerization and kinetic resolution reaction is described. The transformation results in highly enantioenriched bicyclo[3.1.0]hexenes at all levels of conversion, with no racemization or symmetrization taking place during the course of the reaction, and simultaneously affords optically enriched 1,5-enynes. This report marks the first highly enantioselective transformation catalyzed by a well-defined cationic gold(III) catalyst and demonstrates the unique potential of gold(III) complexes in enantioselective catalysis.
- Bohan, Patrick T.,Dean Toste
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supporting information
p. 11016 - 11019
(2017/08/22)
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- Controllable Stereoselective Synthesis of (Z)- and (E)-Homoallylic Alcohols Using a Palladium-Catalyzed Three-Component Reaction
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Diastereoselective synthesis of (Z)- and (E)-homoallylic alcohols using a Pd-catalyzed three-component reaction of 3-(pinacolatoboryl)allyl benzoates, aldehydes, and aryl stannanes was developed, which provides an alternative method for the allylboration of aldehydes using α, γ-diaryl-substituted allylboronates. Both sets of reaction conditions enable access to either (Z)- or (E)-homoallylic alcohols with good to high alkene stereocontrol. The present method showed good functional group compatibility and generality. Efficient chirality transfer reactions to afford enantioenriched (Z)- and (E)-homoallylic alcohols were also achieved.
- Horino, Yoshikazu,Sugata, Miki,Mutsuura, Itaru,Tomohara, Keisuke,Abe, Hitoshi
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supporting information
p. 5968 - 5971
(2017/11/10)
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- The Bull-James assembly as a chiral auxiliary and shift reagent in kinetic resolution of alkyne amines by the CuAAC reaction
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The Bull-James boronic acid assembly is used simultaneously as a chiral auxiliary for kinetic resolution and as a chiral shift reagent for in situ enantiomeric excess (ee) determination by 1H NMR spectroscopy. Chiral terminal alkyne-containing amines, and their corresponding chiral triazoles formed via CuAAC, were probed in situ. Selectivity factors of up to s = 4 were imparted and measured, accurate to within ±3% when compared to chiral GC.
- Brittain, William D. G.,Chapin, Brette M.,Zhai, Wenlei,Lynch, Vincent M.,Buckley, Benjamin R.,Anslyn, Eric V.,Fossey, John S.
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supporting information
p. 10778 - 10782
(2016/12/06)
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- Conjugate Addition of 3-Buytn-2-one to Anilines in Ethanol: Alkene Geometric Insights through in Situ FTIR Monitoring
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A convenient, mild and effective conjugate addition of 3-butyn-2-one to a variety of anilines in ethanol is reported. The reaction was monitored and characterized through in situ FTIR, and the dynamics of the facile E/Z alkene geometry interconversion of the resultant aniline-derived enaminones was explored through NMR, FTIR and X-ray crystallography. A straightforward purification protocol that employs direct Kugelrohr distillation was identified, and the method was further extended to other amines and ynones, allowing rapid access to these interesting compounds.
- Chisholm, David R.,Valentine, Roy,Pohl, Ehmke,Whiting, Andrew
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p. 7557 - 7565
(2016/09/09)
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- Cu-Pybox catalyzed synthesis of 2,3-disubstituted imidazo[1,2-a]pyridines from 2-aminopyridines and propargyl alcohol derivatives
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A highly efficient cascade sequence for syntheses of 2,3-disubstituted imidazo[1,2-a]pyridines with exclusive regioselectivity in moderate to excellent yields has been developed. This cascade was initiated through propargylation of 2-aminopyridines at pyridine-nitrogen with propargyl alcohol derivatives using Cu(II)-Pybox as catalyst and followed by an intramolecular cyclization and isomerization. Besides 2-aminopyridine, less reactive 2-aminopyrimidine, 2-aminopyrazine and 3-aminopyridazine were also suitable in this cascade.
- Cheng, Cang,Ge, Luo,Lu, Xuehe,Huang, Jianping,Huang, Haocheng,Chen, Jie,Cao, Weiguo,Wu, Xiaoyu
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p. 6866 - 6874
(2016/10/04)
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- Ter-pyridine catalyzed allylation of aldehydes and ketones under metal-free condition
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Ter-pyridine derivatives were found to be potential catalyst for homoallylation of carbonyl groups. High yields of the products with short reaction times of ~2 h were observed in several cases. These new catalysts work efficiently with the simple reagent such as allyl magnesium bromide and hence can avoid the use of other sensitive or toxic reagents. It was found that the presence of polar groups on the catalysts made them extremely efficient without the presence of any metal salts.
- Datilus, Vicklyn,Abdulkarim, Mary,Patrizio, Andrew,Kaur, Parminder
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p. 2778 - 2781
(2016/06/09)
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- Highly stereoselective kinetic resolution of α-allenic alcohols: An enzymatic approach
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A highly efficient lipase AK-catalyzed direct kinetic resolution of a variety of α-allenic alcohols was developed. With the complementary to previous studies, the current reaction system is effective on a broad range of substituents (R1) at C(1), such as alkyl, aryl, alkenyl, and alkynyl groups. The Jones-Burgess empirical model was modified to interpret the reversed selectivity during the acetylation of secondary alcohol. The methyl group at C(2) of allenic alcohols implied a small structural adjustment in the catalytic triad of lipase AK, representing a potential direction for future site-directed mutagenesis.
- Li, Wenhua,Lin, Zuming,Chen, Long,Tian, Xuechao,Wang, Yan,Huang, Sha-Hua,Hong, Ran
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supporting information
p. 603 - 606
(2016/01/20)
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- Diversification of ortho-Fused Cycloocta-2,5-dien-1-one Cores and Eight- to Six-Ring Conversion by σ Bond C?C Cleavage
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Sequential treatment of 2-C6H4Br(CHO) with LiC≡CR1(R1=SiMe3, tBu), nBuLi, CuBr?SMe2and HC≡CCHClR2[R2=Ph, 4-CF3Ph, 3-CNPh, 4-(MeO2C)Ph] at ?50 °C leads to formation of an intermediate carbanion (Z)-1,2-C6H4{CA(=O)C≡CBR1}{CH=CH(CH?)R2} (4). Low temperatures (?50 °C) favour attack at CBleading to kinetic formation of 6,8-bicycles containing non-classical C-carbanion enolates (5). Higher temperatures (?10 °C to ambient) and electron-deficient R2favour retro σ-bond C?C cleavage regenerating 4, which subsequently closes on CAproviding 6,6-bicyclic alkoxides (6). Computational modelling (CBS-QB3) indicated that both pathways are viable and of similar energies. Reaction of 6 with H+gave 1,2-dihydronaphthalen-1-ols, or under dehydrating conditions, 2-aryl-1-alkynylnaphthlenes. Enolates 5 react in situ with: H2O, D2O, I2, allylbromide, S2Me2, CO2and lead to the expected C-E derivatives (E=H, D, I, allyl, SMe, CO2H) in 49–64 % yield directly from intermediate 5. The parents (E=H; R1=SiMe3, tBu; R2=Ph) are versatile starting materials for NaBH4and Grignard C=O additions, desilylation (when R1=SiMe) and oxime formation. The latter allows formation of 6,9-bicyclics via Beckmann rearrangement. The 6,8-ring iodides are suitable Suzuki precursors for Pd-catalysed C?C coupling (81–87 %), whereas the carboxylic acids readily form amides under T3P conditions (71–95 %).
- Eccleshare, Lee,Lozada-Rodríguez, Leticia,Cooper, Phillippa,Burroughs, Laurence,Ritchie, John,Lewis, William,Woodward, Simon
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supporting information
p. 12542 - 12547
(2016/08/24)
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- : NBu4NPF6 promoted regioselective cascade synthesis of functionally embellished naphthofurans under acid, metal & solvent free conditions
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nBu4NPF6 mediated highly regioselective synthesis of functionally embellished naphthofurans has been achieved from easily available naphthols and propargyl alcohols through a cascade benzylation, oxacyclisation (5-exo dig) and isomerization under solvent free conditions. The reaction works in a short time through dibenzyl ether formation followed by the decomposition to the carbocation to furnish the high yielding products with large substrate scope. The synthetic utility of the products is demonstrated through C(sp3)-H functionalization. In addition, we investigated selected naphthofurans for their anti-amyloidogenic properties. Preliminary studies suggest that these are excellent inhibitors for amyloid formation, a hallmark for several neurodegenerative diseases.
- Pareek, Abhishek,Dada, Ravikrishna,Rana, Monika,Sharma, Anuj K.,Yaragorla, Srinivasarao
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p. 89732 - 89743
(2016/10/03)
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- Regio- and stereo-selective intermolecular [2+2] cycloaddition of allenol esters with C60 leading to alkylidenecyclobutane-annulated fullerenes
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The intermolecular [2+2] cycloaddition of allenol esters, which were in situ generated by Pt-catalyzed 1,3-acyloxy migration of propargylic esters, with C60 proceeded regio- and stereo-selectively to give a novel class of alkylidenecyclobutane-annulated fullerenes. The cyclobutane-annulated fullerene derivatives have high-lying LUMO levels, which gave a high open-circuit voltage in organic solar cell applications. The observed high electron mobility provided a good fill factor compared with the PCBM-based devices.
- Ueda, Mitsuhiro,Sakaguchi, Tsukasa,Hayama, Miho,Nakagawa, Takafumi,Matsuo, Yutaka,Munechika, Aiko,Yoshida, Shunsuke,Yasuda, Hiroshi,Ryu, Ilhyong
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supporting information
p. 13175 - 13178
(2016/11/09)
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- Styrene as 4π-Component in Zn(II)-Catalyzed Intermolecular Diels-Alder/Ene Tandem Reaction
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A mild Zn-catalyzed intermolecular Diels-Alder/ene tandem reaction with styrene as a 4π-component is reported. A variety of dihydronaphthalene products could be prepared in moderate to good yields. Moreover, a combination of DFT calculations and experiments was performed to further understand the mechanism of this unique tandem reaction.
- Zheng, Min,Wu, Feng,Chen, Kai,Zhu, Shifa
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supporting information
p. 3554 - 3557
(2016/08/16)
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