- Suppression of chemical mutagen-induced SOS response by alkylphenols from clove (Syzygium aromaticum) in the Salmonella typhimurium TA1535/pSK1002 umu test
-
A methanol extract from clove (Syzygium aromaticum) showed a suppressive effect of the SOS-inducing activity on the mutagen 2-(2-furyl)-3-(5-nitro-2-furyl)acrylamide (furylfuramide) in the Salmonella typhimurium TA1535/pSK1002 umu test. The methanol extract was re-extracted with hexane, dichloromethane, ethyl acetate, butanol, and water. The hexane fraction showed a suppressive effect. Suppressive compounds in the hexane fraction were isolated by silica gel column chromatography and identified as trans-isoeugenol (1) and eugenol (2) by GC, GC-MS, IR, and 1H and 13C NMR spectroscopy. Compounds 1 and 2 suppressed the furylfuramide-induced SOS response in the umu test. Compounds 1 and 2 suppressed 42.3 and 29.9% of the SOS-inducing activity at a concentration of 0.60 μmol/mL. These compounds were assayed with other mutagens, 4-nitroquinolin 1-oxide (4NQO) and N-methyl-N′-nitro-N-nitrosoguanidine (MNNG). In addition, compounds 1 and 2 were assayed with aflatoxin B1 (AFB1) and 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), which require liver metabolizing enzymes. These compounds showed suppressive effects of the SOS-inducing activity against furylfuramide, 4NQO, AFB1, and Trp-P-1. To research the structure-activity relationship, methyl esters of 1 and 2 (1Me and 2Me) and o-eugenol (3), as compounds similar to 2, were also assayed with all mutagens. Compounds 1Me, 2Me, and 3 showed weak suppressive effects of the SOS-inducing activity against furylfuramide.
- Miyazawa,Hisama
-
-
Read Online
- Highly Z-Selective Double Bond Transposition in Simple Alkenes and Allylarenes through a Spin-Accelerated Allyl Mechanism
-
Double-bond transposition in alkenes (isomerization) offers opportunities for the synthesis of bioactive molecules, but requires high selectivity to avoid mixtures of products. Generation of Z-alkenes, which are present in many natural products and pharmaceuticals, is particularly challenging because it is usually less thermodynamically favorable than generation of the E isomers. We report a β-dialdiminate-supported, high-spin cobalt(I) complex that can convert terminal alkenes, including previously recalcitrant allylbenzenes, to Z-2-alkenes with unprecedentedly high regioselectivity and stereoselectivity. Deuterium labeling studies indicate that the catalyst operates through a π-allyl mechanism, which is different from the alkyl mechanism that is followed by other Z-selective catalysts. Computations indicate that the triplet cobalt(I) alkene complex undergoes a spin state change from the resting-state triplet to a singlet in the lowest-energy C-H activation transition state, which leads to the Z product. This suggests that this change in spin state enables the catalyst to differentiate the stereodefining barriers in this system, and more generally that spin-state changes may offer a route toward novel stereocontrol methods for first-row transition metals.
- Kim, Daniel,Pillon, Guy,Diprimio, Daniel J.,Holland, Patrick L.
-
supporting information
p. 3070 - 3074
(2021/03/08)
-
- Pd-Catalyzed Tandem Isomerization/Cyclization for the Synthesis of Aromatic Oxazaheterocycles and Pyrido[3,4- b]indoles
-
An effient tandem process consisting of palladium-catalyzed double-bond isomerization of long-chain olefins and subsequent intramolecular cyclization promoted by B2(OH)2 for the synthesis of aromatic oxazaheterocycles is disclosed. This strategy can also provide rapid access to pyrido[3,4-b]indoles, trans-2-olefins, and eneamides bearing various functional groups with high regio- and stereoselectivity.
- Ding, Linglong,Niu, Yan-Ning,Xia, Xiao-Feng
-
p. 10032 - 10042
(2021/07/31)
-
- Facile Synthesis of Chiral Arylamines, Alkylamines and Amides by Enantioselective NiH-Catalyzed Hydroamination
-
Regio- and enantioselective hydroarylamination, hydroalkylamination and hydroamidation of styrenes have been developed by NiH catalysis with a simple bioxazoline ligand under mild conditions. A wide range of enantioenriched benzylic arylamines, alkylamines and amides can be easily accessed by nitroarenes, hydroxylamines and dioxazolones, respectively as amination reagents. The chiral induction in these reactions is proposed to proceed through an enantiodifferentiating syn-hydronickellation step.
- Meng, Lingpu,Yang, Jingjie,Duan, Mei,Wang, You,Zhu, Shaolin
-
supporting information
p. 23584 - 23589
(2021/09/28)
-
- A donor-acceptor complex enables the synthesis of: E -olefins from alcohols, amines and carboxylic acids
-
Olefins are prevalent substrates and functionalities. The synthesis of olefins from readily available starting materials such as alcohols, amines and carboxylic acids is of great significance to address the sustainability concerns in organic synthesis. Metallaphotoredox-catalyzed defunctionalizations were reported to achieve such transformations under mild conditions. However, all these valuable strategies require a transition metal catalyst, a ligand or an expensive photocatalyst, with the challenges of controlling the region- and stereoselectivities remaining. Herein, we present a fundamentally distinct strategy enabled by electron donor-acceptor (EDA) complexes, for the selective synthesis of olefins from these simple and easily available starting materials. The conversions took place via photoactivation of the EDA complexes of the activated substrates with alkali salts, followed by hydrogen atom elimination from in situ generated alkyl radicals. This method is operationally simple and straightforward and free of photocatalysts and transition-metals, and shows high regio- and stereoselectivities.
- Chen, Kun-Quan,Shen, Jie,Wang, Zhi-Xiang,Chen, Xiang-Yu
-
p. 6684 - 6690
(2021/05/31)
-
- Synthesis, antiepileptic effects, and structure-activity relationships of α-asarone derivatives: In vitro and in vivo neuroprotective effect of selected derivatives
-
In the present study, we compared the antiepileptic effects of α-asarone derivatives to explore their structure-activity relationships using the PTZ-induced seizure model. Our research revealed that electron-donating methoxy groups in the 3,4,5-position on phenyl ring increased antiepileptic potency but the placement of other groups at different positions decreased activity. Besides, in allyl moiety, the optimal activity was reached with either an allyl or a 1-butenyl group in conjugation with the benzene ring. The compounds 5 and 19 exerted better neuroprotective effects against epilepsy in vitro (cell) and in vivo (mouse) models. This study provides valuable data for further exploration and application of these compounds as potential anti-seizure medicines.
- Zhang, Jian,Mu, Keman,Yang, Peng,Feng, Xinqian,Zhang, Di,Fan, Xiangyu,Wang, Qiantao,Mao, Shengjun
-
-
- Antibacterial mode of action of the daucus carota essential oil active compounds against campylobacter jejuni and efflux-mediated drug resistance in gram-negative bacteria
-
Today, an alarming rise of bacterial gastroenteritis in humans resulting from consuming Campylobacter-tainted foods is being observed. One of the solutions for mitigating this issue may be the antibacterial activity of essential oils. In the present research, we propose to study the antibacterial activity against Campylobacter and other Gram-negative bacteria of Daucus carota essential oil and its active molecules. In addition, a few chemically synthesized molecules such as (E)-methylisoeugenol, Elemicin, and eugenol were also studied. The results showed that the essential oil itself and its most active component, (E)-methylisoeugenol, exhibited bactericidal effects. Similar effects were detected using purified and chemically synthesized molecules. Also, it was observed that the Daucus carota essential oil and its active molecules affected intracellular potassium and intracellular ATP contents in Campylobacter cells. Inhibition of the membrane bound FO F1-ATPase was also observed. Eventually, for the first time, the efflux mechanism of active molecules of Daucus carota essential oil was also identified in gamma proteobacteria and its specific antibacterial activity against Campylobacter jejuni was associated with the lack of this efflux mechanism in this species.
- Berti, Liliane,Bolla, Jean Michel,Brunel, Jean Michel,Dedieu, Luc,Lorenzi, Vanina,Muselli, Alain
-
-
- ISOMERIZATION OF ALKENES
-
The present invention relates to an isomerization method for alkenes, comprising of reaction an alkene with a Ni(I)-compound. By this method, E-Alkenes are obtained in excellent yield.
- -
-
Page/Page column 20-21
(2020/04/25)
-
- A Next-Generation Air-Stable Palladium(I) Dimer Enables Olefin Migration and Selective C?C Coupling in Air
-
We report a new air-stable PdI dimer, [Pd(μ-I)(PCy2tBu)]2, which triggers E-selective olefin migration to enamides and styrene derivatives in the presence of multiple functional groups and with complete tolerance of air. The same dimer also triggers extremely rapid C?C coupling (alkylation and arylation) at room temperature in a modular and triply selective fashion of aromatic C?Br, C?OTf/OFs, and C?Cl bonds in poly(pseudo)halogenated arenes, displaying superior activity over previous PdI dimer generations for substrates that bear substituents ortho to C?OTf.
- Kundu, Gourab,Rissanen, Kari,Schoenebeck, Franziska,Sperger, Theresa
-
supporting information
p. 21930 - 21934
(2020/10/02)
-
- Method for synthesizing E-methyl styrene compound
-
The method for preparing E-pyridyl or alkyl-substituted,bipyridine, in a solvent, in the presence of nitrogen protection, in, reaction 0 °C -50 °C in the presence of a metal nickel salt 24 - 36h, ligand and an additive is E, and the preparation method disclosed by the invention has the advantages, cheap 2,2 ’ - raw materials, easiness in obtaining 2,2 ’ - and the like. The ligand is,bipyridine or an alkyl-substituted bipyridyl compound, in the. presence of a nitrogen, protection agent, in a solvent.
- -
-
Page/Page column 5; 6
(2020/03/25)
-
- Cobalt-Catalyzed Z to e Isomerization of Alkenes: An Approach to (E)-β-Substituted Styrenes
-
An efficient cobalt-catalyzed Z to E isomerization of β-substituted styrenes using the amido-diphosphine ligand was developed, delivering the (E)-isomers with good functional tolerance and high stereoselectivity. The reaction could be scaled up to gram-scale with a catalyst loading of 0.1 mol %, using a mixture of (Z)- and (E)-alkene as the starting material. Preliminary mechanistic studies indicated that cobalt(I)-hydride and a benzylic-cobalt species were probably involved in the reaction, as supported by experiments and DFT calculations.
- Liu, Hongmei,Xu, Man,Cai, Cheng,Chen, Jianhui,Gu, Yugui,Xia, Yuanzhi
-
supporting information
p. 1193 - 1198
(2020/02/04)
-
- Free Radical Scavenging Activity of Essential Oil of Eugenia caryophylata from Amboina Island and Derivatives of Eugenol
-
Essential oil from Eugenia caryophylata was normally used to heal many different deseaces. Various chemical compositions of essential oil distilled and steamed of Moluccas Eugenia caryophylata has been investigated by many different researchers. Even though an intensive research has been carried out of the local chemotypes, a very detail study has not been fully investigated to find out the complete chemical compounds from the plant essential oil and its content associated with their biological activities. In present paper, we assess the free radical scavenging of E. caryophylata collected from Moluccas islands, Indonesia. Essential oil was extracted from leaves, buds, and stems of plant by steam distillation and analyzed using GC-FID and GC-MS. The result showed that free radical activity of essential oil, main constituent and its derivatives were analized using in vitro method. Essential oil activity from stem obtained as (0.82±0.15 μg/mL) was higher than that from bud and leaf possessing both 1,1-diphenyl-2-picrylhydrazyl (DPPH) and (2,2'-azino-bis-3-ethylbenzthizoline-6-sulphonic acid (ABTS) radical scavenging assays by sinergism of eugenol, eugenyl acetate, β-caryophylene and humulene. The activity of isoeugenol (2) (3.59±0.54 μM) and (5.0±0.53 μM) scavenging DPPH and ABTS, respectively, as derivatives eugenol was higher than (3), (4) and (5). Although (6) was active originally, it was inactive after conversion of the ester. While the change of the double bond of location to conjungation structure caused more activity scavenging radicals than the starting molecule.
- Julianus Sohilait, Hanoch,Kainama, Healthy
-
p. 422 - 428
(2019/08/01)
-
- E-Olefins through intramolecular radical relocation
-
Full control over the selectivity of carbon-carbon double-bond migrations would enable access to stereochemically defined olefins that are central to the pharmaceutical, food, fragrance, materials, and petrochemical arenas. The vast majority of double-bond migrations investigated over the past 60 years capitalize on precious-metal hydrides that are frequently associated with reversible equilibria, hydrogen scrambling, incomplete E/Z stereoselection, and/or high cost. Here, we report a fundamentally different, radical-based approach.We showcase a nonprecious, reductant-free, and atom-economical nickel (Ni)(I)-catalyzed intramolecular 1,3-hydrogen atom relocation to yield E-olefins within 3 hours at room temperature. Remote installations of E-olefins over extended distances are also demonstrated.
- Kapat, Ajoy,Sperger, Theresa,Guven, Sinem,Schoenebeck, Franziska
-
p. 391 - 396
(2019/02/03)
-
- Hydrophilic (ν6-Arene)-Ruthenium(II) Complexes with P-OH ligands as catalysts for the isomerization of allylbenzenes and C-H bond arylation reactions in water
-
Half-sandwich ruthenium(II) complexes containing ν6-coordinated 3-phenylpropanol and phosphinous-acid-type ligands, namely, [RuCl2(ν6-C6H5CH2CH2CH2OH){P(OH)R2}] (R = Me (2a), Ph (2b), 4-C6H4CF3 (2c), 4-C6H4OMe (2d), OMe (2e), OEt (2f), and OPh (2g), have been synthesized in 44-88% yield by reacting [RuCl2{ν6:κ1(O)-C6H5CH2CH2CH2OH}] (1) with the appropriate pentavalent phosphorus oxide R2P(═O)H. The structure of [RuCl2(ν6-C6H5CH2CH2CH2OH){P(OH)Me2}] (2a) was unequivocally confirmed by X-ray diffraction methods. Compounds 2a-g proved to be catalytically active in the isomerization of allylbenzenes into the corresponding (1-propenyl)benzene derivatives employing water as the sole reaction solvent, with [RuCl2(ν6-C6H5CH2CH2CH2OH){P(OH)(OPh)2}] (2g) showing the best performance and a broad substrate scope (73-93% isolated yields with E/Z ratios around 90:10 employing 1 mol % of 2g and 3 mol % of K2CO3, and performing the catalytic reactions at 80 °C for 4-24 h). The results herein presented show for the first time the utility of phosphinous acids as auxiliary ligands for metal-catalyzed olefin isomerization processes, reactions in which a cooperative role for the P - OH unit is proposed. On the other hand, the utility of complexes 2a-g as catalysts for ortho-arylation reactions of 2-phenylpyridine in water is also briefly discussed.
- González-Fernández, Rebeca,Crochet, Pascale,Cadierno, Victorio
-
p. 3696 - 3706
(2019/10/11)
-
- 1-Methyl-1H-tetrazol-5-yl (MT) sulfones in the Julia-Kocienski olefination: Comparison with the PT and the TBT sulfones
-
The stability and the stereoselectivity of newly prepared n-pentyl 1-methyl-1H-tetrazol-5-yl (MT) sulfone 1a in the Julia-Kocienski reactions were compared with those of the PT sulfone 1b and the TBT sulfone 1c. The improved stability of the anion derived from the n-pentyl MT sulfone 1a enhanced the efficiency of the olefination reactions and gave higher yields of the product alkenes 3 compared with the PT sulfone 1b. Especially high E-selectivity and high yields were obtained from the reaction with aromatic aldehydes and α,β-unsaturated aldehydes. The selectivity of 1a was not so sensitive to the change of base counter ion compared with the PT sulfone 1b. The reaction of the MT sulfones having either ethyl or a longer alkyl chain also gave E-alkenes selectively in high yields.
- Ando, Kaori,Kawano, Daiki,Takama, Daiki,Semii, Yutaka
-
p. 1566 - 1569
(2019/05/22)
-
- Radical Cation Diels-Alder Reactions by TiO2 Photocatalysis
-
Radical cation Diels-Alder reactions by titanium dioxide (TiO2) photocatalysis in lithium perchlorate/nitromethane solution are described. TiO2 photocatalysis promotes reactions between electron-rich dienes and dienophiles, which would otherwise be difficult to accomplish due to electronic mismatching. The reactions are triggered by hole oxidation of the dienophile and are completed by the excited electron reduction of the radical cation intermediate at the dispersed surface in the absence of any sacrificial substrate.
- Nakayama, Kaii,Maeta, Naoya,Horiguchi, Genki,Kamiya, Hidehiro,Okada, Yohei
-
supporting information
p. 2246 - 2250
(2019/04/10)
-
- Cobalt-Catalyzed Regioselective Olefin Isomerization under Kinetic Control
-
Olefin isomerization is a significant transformation in organic synthesis, which provides a convenient synthetic route for internal olefins and remote functionalization processes. The selectivity of an olefin isomerization process is often thermodynamically controlled. Thus, to achieve selectivity under kinetic control is very challenging. Herein, we report a novel cobalt-catalyzed regioselective olefin isomerization reaction. By taking the advantage of fine-tunable NNP-pincer ligand structures, this catalytic system features high kinetic control of regioselectivity. This mild catalytic system enables the isomerization of 1,1-disubstituted olefins bearing a wide range of functional groups in excellent yields and regioselectivity. The synthetic utility of this transformation was highlighted by the highly selective preparation of a key intermediate for the total synthesis of minfiensine. Moreover, a new strategy was developed to realize the selective monoisomerization of 1-alkenes to 2-alkenes dictated by installing substituents on the γ-position of the double bonds. Mechanistic studies supported that the in situ generated Co-H species underwent migratory insertion of double bond/β-H elimination sequence to afford the isomerization product. The less hindered olefin products were always preferred in this cobalt-catalyzed olefin isomerization due to an effective ligand control of the regioselectivity for the β-H elimination step.
- Liu, Xufang,Zhang, Wei,Wang, Yujie,Zhang, Ze-Xin,Jiao, Lei,Liu, Qiang
-
supporting information
p. 6873 - 6882
(2018/05/30)
-
- Electronically Mismatched Cycloaddition Reactions via First-Row Transition Metal, Iron(III)-Polypyridyl Complex
-
The iron(III)-polypyridyl complex and its derivatives showed sufficient oxidizing potential to act as a one-electron oxidant, producing radical cations from olefins and promoting the efficient radical cation [2 + 2] and [2 + 4] cycloaddition reactions. Subsequent chain propagation afforded trisubstituted cyclobutane or cyclohexene derivatives, and this facile route enables the replacement of rare metals with sustainable, green, and inexpensive iron in radical cation cycloadditions.
- Shin, Jung Ha,Seong, Eun Young,Mun, Hyeon Jin,Jang, Yu Jeong,Kang, Eun Joo
-
supporting information
p. 5872 - 5876
(2018/09/25)
-
- A General Strategy for Open-Flask Alkene Isomerization by Ruthenium Hydride Complexes with Non-Redox Metal Salts
-
A homogenous metal hydride (M?H) catalyst for isomerization normally requires rigorous air-free techniques. Here, we demonstrate a highly efficient protocol in which simple non-redox metal ions as Lewis acids can promote olefin isomerization dramatically with a commercially available RuH2(CO)(PPh3)3 complex in an open-flask system. Isomerization can be accomplished within a short time, and a satisfactory selectivity for different types of unsaturated compounds can be obtained. Meanwhile, an excellent turnover number up to 17208 was achieved under air, and open-flask gram-scale experiments further demonstrated the efficiency of the RuH2(CO)(PPh3)3/non-redox-metals system. We used FTIR spectroscopy, GC–MS, NMR spectroscopy and kinetics studies to evidence that in the sluggish RuH2(CO)(PPh3)3 catalyst, bloated PPh3 ligands cause steric hindrance for the coordination of the free alkene. Alternatively, the addition of non-redox metal ions could induce the dissociation of the PPh3 ligand to offer unoccupied coordination sites for the alkene and to form the Mg-bridged adduct OC?Ru?H2?Mg2+ as the highly active species, which benefited the isomerization significantly through the metal hydride addition–elimination pathway. Finally, this strategy was demonstrated as an impactful approach for hydride catalysts of other transition metals such as Os.
- Lv, Zhanao,Chen, Zhuqi,Hu, Yue,Zheng, Wenrui,Wang, Haibin,Mo, Wanling,Yin, Guochuan
-
p. 3849 - 3859
(2017/09/18)
-
- Pd-Boron-Catalyzed One Carbon Isomerization of Olefins: Water Assisted Process at Room Temperature
-
A palladium-boronate/borane-system -catalyzed isomerization of olefins has been uncovered. An efficient catalytic combination of [Pd(OAc)2]3-boronate-PCy3-enabled olefin isomerization at 80 °C has been investigated. Addition of water to the reaction showed a remarkable improvement and the isomerization occurred at ambient temperature. These catalytic systems function efficiently for the isomerization of functionalized as well as unfunctionalized olefins. The catalytic conditions demonstrate the involvement of both nonhydride and metal-hydride medium and can be switchable with water as an additive.
- Ojha, Devi Prasan,Gadde, Karthik,Prabhu, Kandikere Ramaiah
-
p. 4859 - 4865
(2017/05/12)
-
- Micellar promoted alkenes isomerization in water mediated by a cationic half-sandwich Ru(II) complex
-
Micellar media in water provide a simple and efficient environment to favor the double bond isomerization of terminal alkenes catalyzed by the cationic half-sandwich complex 1 at 95 °C. The micellar medium favors both catalyst dissolution in water by means of ion-pairing with the preferred anionic surfactants as well as substrate dissolution thus favoring its conversion into products.
- Sperni, Laura,Scarso, Alessandro,Strukul, Giorgio
-
p. 535 - 539
(2016/12/02)
-
- Tunable Photocatalytic Activity of Palladium-Decorated TiO2: Non-Hydrogen-Mediated Hydrogenation or Isomerization of Benzyl-Substituted Alkenes
-
Palladium-decorated TiO2 is a moisture- and air-tolerant versatile catalyst. Its photocatalytic activity can be tuned in favor of hydrogenation or isomerization of benzyl-substituted alkenes simply by changing the irradiation wavelength. Benzyl-substituted alkenes are selectively isomerized to phenyl-substituted alkenes (E-isomer) with complete conversion over Pd@TiO2 under H2-free conditions. The reaction can be thermally induced under air or driven by visible-light irradiation at room temperature under Ar. UV irradiation in methanol solvent leads to efficient hydrogenation. The fine-tunability of the catalyst can also be used for selective deuterium incorporation using deuterated solvents; here H/D exchange is used as a mechanistic tool but with clear potential for isotope substitution applications.
- Elhage, Ayda,Lanterna, Anabel E.,Scaiano, Juan C.
-
p. 250 - 255
(2017/05/31)
-
- Efficient synthesis of functionalized olefins by Wittig reaction using Amberlite resin as a mild base
-
A convenient procedure for the synthesis of olefins by the reaction of stabilized, semistabilized, and nonstabilized phosphorous ylides with various aldehydes or ketone using Amberlite resin as a mild base is described. Our developed method offers facile and racemization-free synthesis of α,β-unsaturated amino esters and chiral allylic amine. The developed methodology offers mild reaction conditions, high efficiency, and facile isolation of the final products, a practical alternative to known procedures.
- Valkute, Tushar R.,Aratikatla, Eswar K.,Bhattacharya, Asish K.
-
p. 581 - 589
(2017/03/15)
-
- Asymmetric Organocatalytic Stepwise [2+2] Entry to Tetra-Substituted Heterodimeric and Homochiral Cyclobutanes
-
An asymmetric synthesis of tetra-substituted cyclobutanes involving an organocatalytic, stepwise [2+2]-cycloaddition is described. The secondary-amine-catalyzed method allows for the hetero-dimerization of two different cinnamic-acid-derived sub-units, opening a novel one-step assembly to densely functionalized, head-to-tail coupled dimeric cyclobutanes in high enantiomeric excess. A series of selective synthetic interconversions in these sensitive cycloadducts is also described.
- Nielsen, Alex J.,Jenkins, Hilary A.,McNulty, James
-
supporting information
p. 9111 - 9115
(2016/07/14)
-
- Direct Olefination of Alcohols with Sulfones by Using Heterogeneous Platinum Catalysts
-
Carbon-supported Pt nanoparticles (Pt/C) were found to be effective heterogeneous catalysts for the direct Julia olefination of alcohols in the presence of sulfones and KOtBu under oxidant-free conditions. Primary alcohols, including aryl, aliphatic, allyl, and heterocyclic alcohols, underwent olefination with dimethyl sulfone and aryl alkyl sulfones to give terminal and internal olefins, respectively. Secondary alcohols underwent methylenation with dimethyl sulfone. Under 2.5 bar H2, the same reaction system was effective for the transformation of alcohol OH groups to alkyl groups. Structural and mechanistic studies of the terminal olefination system suggested that Pt0 sites on the Pt metal particles are responsible for the rate-limiting dehydrogenation of alcohols and that KOtBu may deprotonate the sulfone reagent. The Pt/C catalyst was reusable after the olefination, and this method showed a higher turnover number (TON) and a wider substrate scope than previously reported methods, which demonstrates the high catalytic efficiency of the present method. Olefination of alcohols: The first heterogeneous catalytic terminal and internal olefination of primary alcohols and methylenation of secondary alcohols with sulfones, a reusable carbon-supported Pt catalyst, and KOtBu is reported (see scheme).
- Hakim Siddiki,Touchy, Abeda Sultana,Kon, Kenichi,Shimizu, Ken-Ichi
-
p. 6111 - 6119
(2016/04/26)
-
- Low-Pressure Cobalt-Catalyzed Enantioselective Hydrovinylation of Vinylarenes
-
An efficient and practical protocol for the enantioselective cobalt-catalyzed hydrovinylation of vinylarenes with ethylene at low (1.2 bar) pressure has been developed. As precatalysts, stable [L2CoCl2] complexes are employed that are activated in situ with Et2AlCl. A modular chiral TADDOL-derived phosphine-phosphite ligand was identified that allows the conversion of a broad spectrum of substrates, including heterocyclic vinylarenes and vinylferrocene, to smoothly afford the branched products with up to 99 % ee and virtually complete regioselectivity. Even polar functional groups, such as OH, NH2, CN, and CO2R, are tolerated.
- Movahhed, Sohajl,Westphal, Julia,Dindaro?lu, Mehmet,Falk, Anna,Schmalz, Hans-Günther
-
supporting information
p. 7381 - 7384
(2016/05/24)
-
- A Facile, Convenient, and Green Route to (E)-Propenylbenzene Flavors and Fragrances by Alkene Isomerization
-
(E)-Propenylbenzene flavors and fragrances can be made and isolated in high yield and selectivity by using bifunctional catalyst 1, and the heterogenized analogues. Multigram-scale reactions can be performed neat and the products isolated either by distillation, using homogeneous catalyst 1 (0.1-0.5 mol%, r.t., 10-45 min), or by decantation from heterogeneous catalysts PS-1 or PSL-1 (0.5 mol%, 70 °C, 24 h; catalyst separation and re-use shown for 3-4 cycles; 10 cycles using distilled eugenol feedstock). Both purified starting materials and essential oil feedstocks could be used. Z Isomers were present at very low levels (from 0.4% to less than 0.1%) in the products.
- Larsen, Casey R.,Paulson, Erik R.,Erdogan, Gulin,Grotjahn, Douglas B.
-
supporting information
p. 2462 - 2466
(2015/10/19)
-
- Photooxidizing chromium catalysts for promoting radical cation cycloadditions
-
The photooxidizing capabilities of selected CrIII complexes for promoting radical cation cycloadditions are described. These complexes have sufficiently long-lived excited states to oxidize electron-rich alkenes, thereby initiating [4+2] processes. These metal species augment the spectrum of catalysts explored in photoredox systems, as they feature unique properties that can result in differential reactivity from the more commonly employed ruthenium or iridium catalysts. Spotlight on chromium: Selected CrIII complexes were investigated for promoting radical cation cycloadditions. These species have sufficiently long-lived excited states to oxidize electron-rich alkenes, thereby initiating [4+2] processes. These metal complexes augment the spectrum of catalysts explored in photoredox systems, featuring properties that can result in differential reactivity from the more common Ru or Ir catalysts.
- Stevenson, Susan M.,Shores, Matthew P.,Ferreira, Eric M.
-
supporting information
p. 6506 - 6510
(2015/06/08)
-
- Microwave synthesis of secondary phosphines and phosphine oxides from red phosphorus and allyl(methoxy)benzenes in KOH-DMSO
-
Bis[1-(methoxyphenyl)propan-2-yl]phosphines and bis[1-(methoxyphenyl)propan-2-yl]phosphine oxides were synthesized by phosphorylation of allyl(methoxy)benzenes in the system red phosphorus-KOH · 0.5 H2O-DMSO under microwave irradiation.
- Kuimov,Malysheva,Artem'Ev,Kenzhetaeva,Belogorlova,Komarova,Gusarova,Trofimov
-
p. 1438 - 1442
(2015/02/19)
-
- Iron-catalyzed decarboxylative methylation of α,β-unsaturated acids under ligand-free conditions
-
It is the first time to find that iron-catalyzed decarboxylative methylation of α,β-unsaturated acids could be performed in the absence of any ligands. During the reaction, the configuration of the double bond could be retained. It is noteworthy that di-t
- Rong, Guangwei,Liu, Defu,Lu, Linhua,Yan, Hong,Zheng, Yang,Chen, Jie,Mao, Jincheng
-
p. 5033 - 5037
(2014/12/10)
-
- Iron-catalyzed decarboxylative methylation of α,β-unsaturated acids under ligand-free conditions
-
It is the first time to find that iron-catalyzed decarboxylative methylation of α,β-unsaturated acids could be performed in the absence of any ligands. During the reaction, the configuration of the double bond could be retained. It is noteworthy that di-t
- Rong, Guangwei,Liu, Defu,Lu, Linhua,Yan, Hong,Zheng, Yang,Chen, Jie,Mao, Jincheng
-
p. 5033 - 5037
(2014/07/08)
-
- Synthesis of Z-alkenes from Rh(I)-catalyzed olefin isomerization of β,γ-unsaturated ketones
-
Developing olefin isomerization reactions to reach kinetically controlled Z-alkenes is challenging because formation of trans-alkenes is thermodynamically favored under the traditional catalytic conditions using acids, bases, or transition metals as the catalysts. A new synthesis of Z-alkenes from Rh(I)-catalyzed olefin isomerization of β,γ-unsaturated ketones to α,β-unsaturated ketones was developed, providing an easy and efficient way to access various Z-enones.
- Zhuo, Lian-Gang,Yao, Zhong-Ke,Yu, Zhi-Xiang
-
p. 4634 - 4637
(2013/10/08)
-
- Eugenol isomerization promoted by arene-ruthenium(ii) complexes in aqueous media: Influence of the pH on the catalytic activity
-
The catalytic activity of the arene-ruthenium(ii) complexes [RuCl 2(η6-C6H5OCH2CH 2OH)(L)] (L = P(OMe)3 (1a), P(OEt)3 (1b), P(OiPr)3 (1c), P(OPh)3 (1d), PPh3 (1e)) in the isomerization of eugenol into isoeugenol has been evaluated. Best results in terms of activity and selectivity were observed with those catalysts containing an aliphatic P-donor ligand (1a-c). Under optimized conditions, full conversions in extremely short reaction times (5 min), and with high levels of trans-selectivity (up to 98%), could be achieved. Addition of both NaOH or H2SO4 to the aqueous media resulted in rate enhancements, suggesting two different activation pathways of the pre-catalysts. We have evidenced that sodium hydroxide promotes the release of the η6- coordinated arene ligand, while sulfuric acid favours the Ru-Cl bond dissociation and the formation of aquo-derivatives [RuCl(H2O) (η6-C6H5OCH2CH 2OH)(L)][Cl]. The Royal Society of Chemistry 2013.
- Lastra-Barreira, Beatriz,Diaz-Alvarez, Alba E.,Menendez-Rodriguez, Lucia,Crochet, Pascale
-
p. 19985 - 19990
(2013/11/06)
-
- Enantioselective nickel-catalyzed hydrocyanation of vinylarenes using chiral phosphine-phosphite ligands and TMS-CN as a source of HCN
-
Anti-headache chemistry: In the presence of a tailored modular P,P ligand the nickel-catalyzed addition of HCN, generated in situ from TMS-CN, to styrene derivatives proceeds with an unprecedented level of stereocontrol (up to 97 % ee) to give 2-aryl-acetonitriles, for example, the depicted precursor of Ibuprofen. Copyright
- Falk, Anna,Goederz, Anna-Lena,Schmalz, Hans-Guenther
-
supporting information
p. 1576 - 1580
(2013/03/13)
-
- Synthesis of [2-(methoxyaryl)-1-methylethyl]phosphinic acids from red phosphorus and (allyl)(methoxy)benzenes
-
(Allyl)(methoxy)benzenes react with red phosphorus in the superbasic system KOH-DMSO in the presence of small amounts of water and hydroquinone (3 h, 130 C) to regio- and chemoselectively give [2-(methoxyaryl)-1-methylethyl]phosphinic acids in preparative yields up to 52%. The reactions involve isomerization of allylbenzenes into (prop-1-enyl)benzenes.
- Malysheva,Kuimov,Artem'Ev,Belogorlova,Albanov,Gusarova,Trofimov
-
p. 1787 - 1791
(2013/11/19)
-
- Modular palladium bipyrazoles for the isomerization of allylbenzenes - Mechanistic considerations and insights into catalyst design and activity, role of solvent, and additive effects
-
The catalytic activity of novel bidentate N,N-chelated palladium complexes derived from electron excessive, backbone fused 3,3'-bipyrazoles in the selective isomerization of terminal arylpropenoids and 1-alkenes is described. The catalysts are easily modified by appropriate wing tip substitution, while maintaining the same bulky, rigid unreactive aliphatic backbone. Eleven novel palladium complexes with different electronic and steric properties were investigated. Their performance in the palladium(II)-catalyzed isomerization of a series of substituted allylbenzenes was evaluated in terms of electronic as well as steric effects. Besides the clear finding of a general trend towards higher catalyst activity with more electron-donating properties of the coordinated N,N-bidentate ligands, we found that the catalytic process strongly depends on the choice of solvents and additives. Extensive solvent screening revealed that reactions run best in a 2:1 toluene-methanol mixture, with the alcohol employed being a crucial factor in terms of electronic and steric factors. A reaction mechanism involving a hydride addition-elimination mechanism starting with a palladium hydride species generated in situ in alcoholic solutions, as corroborated by experiments using deuterium labeled allylbenzene, seems to be most likely. The proposed mechanism is also supported by the observed reaction rate orders of κobs[cat.]≈1 (0.94), κobs [substrate]=0.20→1.0 (t→∞) and κobs [methanol]=-0.51 for the isomerization of allylbenzene. Furthermore, the influence of acid and base, as well as the role of the halide coordinated to the catalyst, are discussed. The system catalyzes the isomerization of allylbenzenes very efficiently yielding high E:Z selectivities under very mild conditions (room temperature) and at low catalyst loadings of 1 mol% palladium even in unpurified solvents. The integrity and stability of the catalyst system were confirmed by multiple addition reaction cycles, successive filtration and isolation experiments, and the lack of palladium black formation. Copyright
- Spallek, Markus J.,Stockinger, Skrollan,Goddard, Richard,Trapp, Oliver
-
experimental part
p. 1466 - 1480
(2012/09/11)
-
- Highly active and selective platinum(II)-catalyzed isomerization of allylbenzenes: Efficient access to (E)-anethole and other fragrances via unusual agostic intermediates
-
Terminal alkene isomerization reactions can be efficiently catalyzed by PtII complexes bearing a chelating diphosphine and an alkyl or, better, aryl moiety under mild experimental conditions. In particular diphosphines, such as dppb, characterized by a large bite angle in conjunction with a pentafiuorophenyl residue coordinated to Pt enable quantitative conversion of the reagent into internal, alkenes within few hours at 50 °C in CHCl3 as solvent. E/Z selectivity can be as high as 98:2 for allylbenzene, and the catalytic system can be fruitfully applied to the preparation of E fragrances derived by isomerization of substituted, allylbenzene derivatives. The selectivity increases during the progress of the reaction because of a subsequent catalytic step where the Z alkene coordinates to the Pt and is converted into the E isomer. NMR investigation on the catalyst showed formation of agostic Pt...H intermediate species derived by insertion of the substrate into the Pt-aryl bond followed by β-hydride elimination. Formation of such agostic species is promoted by the steric hindrance imparted by the diphosphine characterized by a large bite angle. Kinetic studies and DFT calculations on the possible agostic intermediates shed light on their structure and enable the formulation of a possible catalytic mechanism.
- Scarso, Alessandro,Colladon, Marco,Sgarbossa, Paolo,Santo, Claudio,Michelin, Rino A.,Strukul, Giorgio
-
experimental part
p. 1487 - 1497
(2010/05/15)
-
- First green protocols for the large-scale preparation of γ-diisoeugenol and related dihydro(1H)indenes via formal [3+2] cycloaddition reactions
-
Trans-isoeugenol and related styrenes (trans-isohomogenol or O-benzylated isoeugenol), important components of the essential oil of various tropical plants, dimerize easily in the presence of catalytic amounts of BF3·OEt2 in poly(ethylene glycol) with Mn = 400 (PEG-400) or SiO2-OSO3H in MeCN via formal [3+2] cycloaddition reaction to give respective natural products (diisoeugenol and its O-substituted analog) with the 1,2-trans-2,3-trans-configuration in excellent yields. γ-Diisoeugenol scale-up preparation has also been described.
- Kouznetsov, Vladimir V.,Merchan Arenas, Diego R.
-
body text
p. 1546 - 1549
(2009/06/21)
-
- Fast and green microwave-Assisted conversion of essential oil allylbenzenes into the corresponding aldehydes via alkene isomerization and subsequent potassium permanganate promoted oxidative alkene group cleavage
-
Essential oil allylbenzenes from have been converted quickly and efficiently into the corresponding benzaldehydes in good yields by a two-step "green" reaction pathway based on a solventless alkene group isomerization by KF/Al2O3 to form the corresponding l-arylpropene and a subsequent solventless oxidation of the latter to the corresponding benzaldehyde by KMnO4/CuSO4-5H2O. The assistance by microwave irradiation results in very short reaction times (2O3 under solvent-free conditions, respectively.
- Luu, Thi Xuan Thi,Lam, Trinh To,Le, Thach Ngoc,Duus, Fritz
-
experimental part
p. 3411 - 3424
(2010/01/16)
-
- Neutral ionic liquid [hmim]Br as a green reagent and solvent for the mild and efficient dehydration of benzyl alcohols into (E)-arylalkenes under microwave irradiation
-
A mild and efficient, ionic-liquid-assisted, green protocol for the dehydration of benzyl alcohols into the corresponding (E)-arylalkenes under microwave irradiation has been developed. The method utilizes a neutral and recyclable ionic liquid (1-hexyl-3-methylimidazolium bromide) as a reagent and solvent to cleanly provide a wide range of olefins without the need of harsh and expensive Bronsted/Lewis acids. The method was extended to the efficient conversion of acetylated/benzoylated derivatives of benzyl alcohol into their corresponding (E)-arylalkenes. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Kumar, Rakesh,Sharma, Abhishek,Sharma, Naina,Kumar, Vinod,Sinha, Arun K.
-
supporting information; experimental part
p. 5577 - 5582
(2009/05/11)
-
- Process for the Isomerisation of Alkenyl Alkoxybenzenes
-
A process for the catalytic double bond isomerisation of alkenyl alkoxybenzenes [alkoxy-substituted (2-alkenyl)-benzenes] (with a non-conjugated double bond in the alkenyl group) of formula A in the presence of a catalytically active quantity of alkali and/or alkaline earth C1-C6 alcoholates to the corresponding alkenyl alkoxybenzenes [alkoxy-substituted (1-alkenyl)-benzenes] (with a double bond in the alkenyl group which is conjugated with the benzene ring) of formula B is described
- -
-
Page/Page column 4
(2008/06/13)
-
- Proazaphosphatrane P(RNCH2CH2)3N (R = Me, i-Pr)-catalyzed isomerization of allylaromatics, allyl phenyl sulfide, allyl phenyl sulfone, and bis-allymethylene double bond-containing compounds
-
Using a proazaphosphatrane catalyst, P(RNCH2CH2) 3N (R = Me, i-Pr), allylaromatics and allyl phenyl sulfide were selectively isomerized to the corresponding vinyl isomers in yields up to > 99% in CH3CN at 40°C. Efficient transformation of allyl phenyl sulfone at ambient temperature afforded an isomerization/dimerization product in >95% yield. Conjugation of bis-allylmethylene double bond-containing compounds gave the corresponding conjugated isomers for cis,cis-9,12- octadecadienol and its methyl ether in yields up to 97%, and desilylation/conjugation products were obtained from the catalytic reaction of the trimethylsilyl ether of cis,cis-9,12-octadecadienol. The reaction mechanism is discussed based upon the 1H and 31P NMR-monitored reactions in CD3CN or CH3CN under the reaction conditions.
- Yu, Zhengkun,Yan, Shenggang,Zhang, Guangtao,He, Wei,Wang, Liandi,Li, Yu,Zeng, Fanlong
-
p. 111 - 117
(2007/10/03)
-
- Dehydrozingerone, chalcone, and isoeugenol analogues as in vitro anticancer agents
-
Twenty-eight compounds related to dehydrozingerone (1), isoeugenol (3), and 2-hydroxychalcone (4) were synthesized and evaluated in vitro against human tumor cell replication. Except for isoeugenol analogues 27-35, most compounds exhibited moderate or strong cytotoxic activity against KB, KB-VCR (a multidrug-resistant derivative), and A549 cell lines. In particular, chalcone 15 showed significant cytotoxic activity against the A549 cell line with an IC50 value of 0.6 μg/mL. Furthermore, dehydrozingerone analogue 11 and chalcones 16 and 17 showed significant and similar cytotoxic activity against both KB (IC50 values of 2.0, 1.0, and 2.0 μg/mL, respectively) and KB-VCR (IC50 values of 1.9, 1.0, and 2.0 μ/mL, respectively) cells, suggesting that they are not substrates for the P-glycoprotein drug efflux pump.
- Tatsuzaki, Jin,Bastow, Kenneth F.,Nakagawa-Goto, Kyoko,Nakamura, Seiko,Itokawa, Hideji,Lee, Kuo-Hsiung
-
p. 1445 - 1449
(2008/12/21)
-
- Methoxy-substituted stilbenes, styrenes, and 1-arylpropenes: Photophysical properties and photoadditions of alcohols
-
The photochemistry of trans-stilbene and four methoxy-substituted stilbene derivatives has been investigated in a variety of solvents. The fluorescence of all five trans isomers was quenched by 2,2,2-trifluoroethanol (TFE). Upon irradiation of the five substrates in TFE, the products derived from photoaddition of the solvent were detected. Nuclear magnetic resonance spectroscopy of the products formed by irradiation in TFE-OD indicated that the proton and nucleophile are attached to two adjacent atoms of the original alkene double bond. Irradiation of the corresponding methoxy-substituted styrenes and trans-1-arylpropenes in TFE produced the analogous solvent adducts. The photoaddition of TFE proceeded with the general order of reactivity: styre > trans-1-arylpropenes > trans-stilbenes. Transient carbocation intermediates were observed following laser flash photolysis of the stilbenes in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). The results are consistent with a mechanism that involves photoprotonation of the substrates by TFE or HFIP, followed by nucleophilic trapping of short-lived carbocation intermediates. Compared to the other stilbene derivatives, trans-3,5-dimethoxystilbene displayed a large quantum yield of fluorescence and a low quantum yield of trans-cis isomerization in polar organic solvents. The unique photophysical properties of trans-3,5-dimethoxystilbene are attributed to formation of a highly polarized charge-transfer excited state (μe = 13.2 D).
- Roberts, Jeffrey C.,Pincock, James A.
-
p. 1480 - 1492
(2007/10/03)
-
- Ultrasound-assisted convenient synthesis of hypolipidemic active natural methoxylated (E)-arylalkenes and arylalkanones
-
An ultrasound-assisted convenient method was developed for the conversion of toxic methoxylated cis-isomer of arylalkenes into its hypolipidemic active trans-isomer. Treatment of cis-isomer or mixture of all three isomers (1a-1j) with ammonium formate and 10% Pd/C gave arylalkanes (2a-2j), which upon oxidation with DDQ in anhydrous dioxane containing a little amount of silica gel, provided (E)-arylalkenes (3a-3g) in 42-72% yield depending upon the substituents attached at the aryl ring. The same method, upon addition of a few drops of water, provided hypolipidemic active arylalkanones (3h-3j) in 59-65% yield.
- Joshi, Bhupendra P.,Sharma, Anuj,Sinha, Arun K.
-
p. 3075 - 3080
(2007/10/03)
-
- An effective system to synthesize hypolipidemic active α-asarone and related methoxylated (E)-arylalkenes
-
Methoxylated (E)-arylalkenes (1a-1k) were prepared in two steps by an improved Grignard reaction comprising the reverse addition of alkylmagnesium bromide to benzaldehydes (2a-2k) in anhydrous ether and toluene into arylalkanols (3a-3k) in high yield, followed by dehydration with silica gel under microwave irradiation for 3-12 min, depending upon the substituents attached to the aromatic ring to afford hypolipidemic active α-asarone (1a) and related methoxylated (E)-arylalkenes (1b-1k).
- Sharma, Anuj,Joshi, Bhupendra P.,Sinha, Arun K.
-
p. 2231 - 2235
(2007/10/03)
-
- A concise synthesis of carpanone using solid-supported reagents and scavengers
-
The synthesis of the natural product carpanone by utilization of polymer supported reagents, eliminating the need for conventional purification techniques was reported. The synthesis and crystal structure of a polymer-supported iridium catalyst for isomerization was also reported. The observations showed that isomerization of electron-rich aromatic compounds by the catalyst resulted in products with predominantly trans alkene geometry. However, the electron-poor derivatives were found to be less prone to rearrangement.
- Baxendale, Ian R.,Lee, Ai-Lan,Ley, Steven V.
-
p. 1850 - 1857
(2007/10/03)
-
- A polymer-supported iridium catalyst for the stereoselective isomerisation of double bonds
-
A polymer-supported iridium catalyst has been prepared and used in the isomerisation of the double bonds in aryl allylic derivatives with excellent trans selectivity and without the need for conventional work-up procedures.
- Baxendale, Ian R.,Lee, Ai-Lan,Ley, Steven V.
-
p. 516 - 518
(2007/10/03)
-
- Development of a polymer bound Wittig reaction and use in multi-step organic synthesis for the overall conversion of alcohols to β-hydroxyamines
-
An efficient combinatorial access to β-hydroxyamines suitable for automation is achieved by the mild oxidation of alcohols to aldehydes by polymer supported perruthenate (PSP), the subsequent clean olefination of the obtained aldehydes by polymer supported Wittig reagents followed by the epoxidation of the olefins by dimethyldioxirane (DMDO), and the final aminolysis of the epoxides with various amines is described.
- Bolli, Martin H.,Ley, Steven V.
-
p. 2243 - 2246
(2007/10/03)
-
- Olefination of activated halides and mesylates using arsonium ylides
-
Alkyltriphenylarsonium ylides react with activated primary halides and mesylates to afford olefins in good yields and with high E-selectivity.
- Seyer, Andre,Alcaraz, Lilian,Mioskowski
-
p. 7871 - 7874
(2007/10/03)
-