- A fortuitously straightforward synthesis of 4-acetoxy-2-propyltetrahydrothiophene
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4-Acetoxy-2-propyltetrahydrothiophene was synthesised from 1-hepten-4-ol by a three-step route involving epoxidation and mesylation to 1,2-epoxy-4-heptyl mesylate and then reaction with thioacetate. An acetoxylated cyclic product was formed instead of the expected thioacetate, and a mechanism for its formation using an intramolecular transesterification is proposed.
- Ma, Bianbian,Yang, Shaoxiang,Tao, Feiyan,Sun, Baoguo,Liu, Yongguo,Tian, Hongyu
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Read Online
- Synthesis of a new odourant, 2-mercapto-4-heptanol
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2-Mercapto-4-heptanol is a relatively new flavour compound that was recently approved as an ingredient by the Flavour and Extract Manufacturers' Association in 2013. Its synthesis, which we have accomplished in four-steps, involved firstly a Grignard reaction of n-butanal with allylmagnesium chloride to prepare 1-hepten-4-ol. This was epoxidised and then converted to 1,2-epithio-4-heptanol, reduction of which with LiAlH4 gave the target compound in an overall yield of about 54%.
- Yang, Shaoxiang,Gong, Wei,Sun, Baoguo,Liu, Yongguo,Tian, Hongyu
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Read Online
- Toward creation of a universal NMR database for stereochemical assignment: The case of 1,3,5-trisubstituted acyclic systems
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Using the diastereoisomeric triols 1a-d (Fig. 1) and examples summarized in Fig. 2, the central C-atom of acyclic 1,3,5-triols is demonstrated to exhibit a distinctive chemical shift that is dependent on the 1,3- and 3,5-relative configuration, but is independent of the functionalities present outside of this structural motif. These NMR characteristics are then used to predict the relative configuration of several natural products (Fig, 7). In addition, an example is given to show the possibility of assembling an NMR database for a larger array of functional groups from NMR databases of smaller arrays of functional groups.
- Kobayashi, Yoshihisa,Tan, Choon-Hong,Kishi, Yoshito
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Read Online
- Method for synthesizing 8th-site substituted-3,4,7,8-tetrahydro-2H-oxocin-2-one octatomic ring
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The invention discloses a method for synthesizing 8th-site substituted-3,4,7,8-tetrahydro-2H-oxocin-2-one octatomic ring. The synthesis method includes the following steps: performing Grignard reaction on an aldehyde or ketone to obtain an allyl alcohol compound; and performing condensation reaction with 2-(tert-butylsulfonyl)acetic acid to obtain an allyl (tert-butylsulfonyl)acetate compound; performing olefin cross-metathesis reaction under the action of a second generation Grubbs catalyst to obtain a methoxycarbonyl (tert-butylsulfonyl)acetate compound; performing intramolecular reaction byusing anhydrous N,N-dimethylformamide as a solvent in the presence of a catalyst palladium acetate and a ligand triphenylphosphine, so as to produce a 3-tert-butylsulfonyl 8th-site substituted-3,4,7,8-tetrahydro-2H-oxocin-2-one octatomic ring lactone compound; and finally removing tert-butylsulfonyl in a reaction solution of sodium amalgam and acetic acid by taking ethanol as a solvent, so as toobtain 8th-site substituted-3,4,7,8-tetrahydro-2H-oxocin-2-one octatomic ring lactone compound. The yield of the method is high, and a solution with a very dilute reaction concentration is not neededin the synthesis of various substituted octatomic ring lactones through intramolecular catalysis by palladium, so the process conditions are simple and universal.
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Paragraph 0018-0023; 0025
(2019/10/01)
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- Oxa/thiazole-tetrahydropyran triazole-linked hybrids with selective antiproliferative activity against human tumour cells
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Inspired by diverse marine bioactive compounds, the principle of molecular hybridization was applied to produce a series of new compounds combining diverse heterocyclic systems (oxa/thiazoles and tetrahydropyrans) via a triazole ring, attempting to increase the activity of individual building blocks. These new compounds exhibit a highly interesting antiproliferative activity against different human tumour cells and good selectivity when compared to normal cells. The formation of reactive oxygen species and the interaction with P-gp were also evaluated for the lead compounds.
- Valdomir, Guillermo,Fernández,Lagunes, Irene,Padrón, Juan I.,Martín, Víctor S.,Padrón, José M.,Davyt, Danilo
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supporting information
p. 13784 - 13789
(2018/08/21)
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- Enantio- and Diastereoselective Synthesis of 1,5-syn-(Z)-Amino Alcohols via Imine Double Allylboration: Synthesis of trans-1,2,3,6-Tetrahydropyridines and Total Synthesis of Andrachcine
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A stereoselective synthesis of trans-1,2,3,6-tetrahydropyridines 8 is described. This synthesis proceeds via intramolecular Mistunobu reactions of 1,5-syn-(Z)-amino alcohols 7, which were prepared by a highly diastereo- and enantioselective double-allylboration reaction of aldehyde 5 and silylimine 6. The chiral bifunctional γ-borylallylborane 9E was generated in situ by hydroboration of allene 3 with (diisopinocampheyl)borane 4. This strategy was applied to the total synthesis of andrachcine 1, thus establishing with certainty the absolute and relative configuration of the natural product.
- Allais, Christophe,Roush, William R.
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supporting information
p. 2646 - 2649
(2017/05/24)
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- Synthesis of homoallylic amines and acylhydrazides by tin powder-promoted multicomponent one-pot allylation reactions
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An efficient process for the synthesis of homoallylic amines and N′-homoallylic hydrazides is developed from the one-pot reaction of carbonyl compounds, amines or N-acylhydrazines, allyllic bromide and tin powder using water as solvent. N-Acylhydrazines are found to be more reactive than amines in these processes. They can react not only with aldehydes but also with ketones to give the corresponding N′-homoallylic hydrazides. Copyright
- Ma, Junyan,Huang, Danfeng,Wang, Ke-Hu,Xu, Yanli,Chong, Siying,Su, Yingpeng,Fu, Ying,Hu, Yulai
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p. 571 - 576
(2016/07/16)
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- A ionic the bistriphenyl make PVC possess enough preparation and application of (V) complex
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The invention provides a preparation method of an ionic type bis-triphenyl organic antimony (V) complex and a method for synthesizing allyl alcohol compounds under catalysis of the ionic type bis-triphenyl organic antimony (V) complex. The complex is a cationic type organic antimony complex, wherein two antimony atoms in the complex are bridged by virtue of oxygen atoms and are pentavalent; and each antimony atom is in coordination with one water molecule, and an ionic bond is formed by the entire organic antimony cationic part with corresponding anions. The synthetic method comprises the following step: by taking the bis-triphenyl organic antimony (V) complex as a catalyst, taking a commonly-used organic solvent as a reaction solvent, and taking aldehyde and tetraallyltin as raw materials, performing reaction. The synthetic method can be used for providing a novel low-cost and 'green' route for preparing the allyl alcohol compounds, and has the advantages that target product selectivity and yield are high, the catalyst can be repeatedly used, corresponding ketone can be obtained by performing simple column chromatography separation on the product, and the whole reaction and separation process is simple to operate and is green and environment-friendly.
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Paragraph 0068; 0069
(2017/01/02)
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- Short stereoselective synthesis of (+)-monocerin via a palladium-catalysed intramolecular alkoxycarbonylation
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A concise stereoselective total synthesis of (+)-monocerin has been accomplished using cross metathesis, tandem dihydroxylation-SN2 cyclisation and intramolecular alkoxycarbonylation as key steps. Cross-metathesis of 2-iodo-3,4,5-trimethoxyvinylbenzene and (R)-hepten-4-ol, followed by tandem dihydroxylation-SN2 cyclisation generated a tri-substituted tetrahydrofuran ring. Finally, the dihydroisocoumarin was obtained by an intramolecular alkoxycarbonylation. In this paper, we have developed an expedient operationally simple Pd(OAc)2/bathocuproine catalysed alkoxycarbonylation under atmospheric pressure of carbon monoxide. The catalytic system developed here can be useful for the synthesis of various dihydroisocoumarins and phthalides.
- Punganuru, Surendra R.,Aviraboina, Sivaprasad,Srivenugopal, Kalkunte S.
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p. 375 - 378
(2016/07/06)
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- Synthesis of active tin: An efficient reagent for allylation reaction of carbonyl compounds
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High purity Sn(0) has been obtained as a result of reduction of SnO by sodium stannite (Na2SnO2) in aqueous solution. The process stands unique for the production of tin metal. The as-synthesized tin finds applications in synthetic organic chemistry as a reagent for the allylation of aldehydes and ketones in distilled water at room temperature to give rise to the corresponding homoallylic alcohols with high yield. The reaction occurs without the assistance of heat, ultrasonic vibration, co-solvents/co-reagents, etc. Enhancement of the reaction rate of allylation was observed in water rather than THF. The manipulation of allylation reaction becomes easy with active tin material.
- Sinha, Arun Kumar,Sil, Amit,Sasmal, Anup Kumar,Pradhan, Mukul,Pal, Tarasankar
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p. 1685 - 1690
(2015/03/30)
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- Strong Lewis acids of air-stable binuclear triphenylantimony(V) complexes and their catalytic application in C-C bond-forming reactions
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Two air-stable novel Lewis acids of triphenylantimony(V) pentafluorbezenesulfonates (2) and perfluorooctanesulfonates (3) were successfully synthesized and characterized. X-ray studies and thermo-gravimetric analysis found that these complexes showed high anti-hydrolyzability and thermal stability. The high catalytic activity and excellent recyclability of these complexes were achieved in the Michael addition reaction and the allylation reaction. On account of their stability, storability, as well as catalytic efficiency, these complexes should find a broad range of utility in organic synthesis.
- Li, Ningbo,Qiu, Renhua,Zhang, Xiaohong,Chen, Yun,Yin, Shuang-Feng,Xu, Xinhua
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p. 4275 - 4281
(2015/06/08)
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- Hydroxyl group-assisted palladium-catalyzed lactonization of homoallylic alcohols
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A convenient and highly efficient synthesis of α-methylene-γ- lactones through the palladium(II)-catalyzed lactonization of homoallylic alcohols with alkynamides has been reported. The hydroxyl group in the terminal olefins cooperates with the amide in alkynamides to promote the cyclization by suppressing the β-H elimination. This process provides a route to construct naturally occurring biologically multifunctional α-methylene-γ- lactones. The time has come to.i?lactonize: α-Methylene- γ-lactones are synthesized through the PdII-catalyzed lactonization of homoallylic alcohols with alkynamides. The hydroxyl group in the terminal olefins cooperates with the amide in alkynamides to promote the cyclization by suppressing the β-H elimination. This provides a route towards naturally occurring biologically multifunctional α-methylene- γ-lactones. Copyright
- Huang, Liangbin,Wang, Qian,Wu, Wanqing,Jiang, Huanfeng
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p. 561 - 566
(2014/03/21)
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- Stereoselective total synthesis of the (Z)-isomer of a novel phytotoxic nonenolide from Phomopsis sp. HCCB03520 and its C-6 epimer
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The (Z)-isomer of a phytotoxic nonenolide, (6S,7R,9R)-6,7-dihydroxy-9- propylnon-4-eno-9-lactone isolated from Phomopsis sp. HCCB03520 and its C-6 epimer have been synthesized through a common route starting from butyraldehyde. The synthesis involves enantioselective Maruoka allylation, Sharpless asymmetric epoxidation and intramolecular ring closing metathesis as the important steps.
- Reddy, Cheruku Ravindra,Das, Biswanath
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- Periodic ethylene-vinyl alcohol copolymers via ADMET polymerization: Synthesis, characterization, and thermal property
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Periodic copolymers of ethylene and vinyl alcohol (EVA) were synthesized via acyclic diene metathesis (ADMET) polymerization of a series of structurally symmetric α,ω-diene monomers that containing two vinyl acetate (VAc) units, followed by exhaustive hydrogenation and subsequent hydrolysis. This synthetic methodology provided a new type of EVA copolymer with defined sequence and ever highest VA content via ADMET. These polymer samples were characterized by gel permeation chromatography (GPC), NMR, and matrix-assisted laser desorption/ionization time-of-fight mass spectroscopy (MALDI-TOF-MS). Thermal properties of EVAc and EVA copolymers were investigated by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). EVAc copolymers exhibited two-stage decompositions on TGA traces and displayed a glass transition on DSC thermograms. Meanwhile, the EVA copolymers showed glass transition stages and sharp melting peaks on DSC thermograms, with the T m values being comparable to that of high density polyethylene (HDPE).
- Li, Zi-Long,Lv, An,Li, Lei,Deng, Xin-Xing,Zhang, Li-Jing,Du, Fu-Sheng,Li, Zi-Chen
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p. 3841 - 3849
(2013/07/26)
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- 2H-pyran-2-ones from trichoderma viride and trichoderma asperellum
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Volatiles emitted by the soil fungi Trichoderma viride 272 and Trichoderma asperellum 328 were collected by using the closed loop stripping analysis (CLSA) headspace technique, and the obtained extracts were analysed by GC/MS. Several alkyl- and alkenyl-2H-pyran-2-ones, including known compounds 6-pentyl-2H-pyran-2-one and (E)-6-(pent-1-en-1-yl)-2H-pyran-2-one, and the new derivatives (E)-6-(pent-2-en-1-yl)-2H-pyran-2-one, 6-propyl-2H-pyran-2-one, and 6-heptyl-2H-pyran-2-one were found. The alkenyl derivative (E)-6-(hept-1-en-1- yl)-2H-pyran-2-one, previously tentatively identified from a marine Botrytis by MS analysis, was also detected. All alkenyl pyrones were synthesised by using a reported Stille coupling followed by lactonisation, whereas the alkylated pyrones were obtained through a reported synthetic approach by radical bromination of 5-alkylpent-2-en-5-olides and dehydrobromination. Because the yields in both cases were not satisfactory and fell a long way short of the yields reported for similar compounds, all compounds were synthesised again using a gold-catalysed coupling of terminal alkynes with propiolic acid recently developed by Schreiber and co-workers, giving high yields in all cases. A comparison of the synthetic methods is given. Copyright
- Wickel, Susanne M.,Citron, Christian A.,Dickschat, Jeroen S.
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p. 2906 - 2913
(2013/06/27)
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- Study on the coupling of acyclic esters with alkenes - The synthesis of 2-(2-hydroxyalkyl)cyclopropanols via cascade cyclization using allylsamarium bromide
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The radical cyclization between aliphatic acyclic esters and alkenes was achieved unprecedentedly in the presence of allylsamarium bromide with HMPA and H2O as additives. The cascade radical cyclization-ring-opening- anionic cyclization allowed facile and efficient access to 2-(2-hydroxyalkyl) cyclopropanols from readily available materials.
- Tu, Yawei,Zhou, Liejin,Yin, Ruifeng,Lv, Xin,Flowers Ii, Robert A.,Choquette, Kimberly A.,Liu, Huili,Niu, Qingsheng,Wang, Xiaoxia
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supporting information
p. 11026 - 11028
(2013/01/15)
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- The first stereoselective total synthesis of putaminoxin e and its epimer and evaluation of their biological properties
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Putaminoxin E, a natural nonanolide, and its C-9 epimer were synthesized for the first time starting from pentane-1,5-diol and butyraldehyde. The synthetic sequences involve Maruoka asymmetric allylation, Sharpless kinetic resolution, and ring-closing metathesis as the key steps. The cytotoxic and antimicrobial activities of these compounds were evaluated. Putaminoxin E, a natural nonanolide, and its C-9 epimer were synthesized for the first time starting from pentane-1,5-diol and butyraldehyde. Copyright
- Sudhakar, Chithaluri,Reddy, Parigi Raghavendar,Kumar, Chityal Ganesh,Sujitha, Pombala,Das, Biswanath
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experimental part
p. 1253 - 1258
(2012/04/10)
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- Total synthesis of 2-(2-hydroxyalkyl)-piperidine alkaloids (-)-halosaline and (-)-8-epi-halosaline via iterative asymmetric allylation/RCM strategy
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Total synthesis of 2-(2-hydroxyalkyl)-piperidine alkaloids, (-)-halosaline and (-)-8-epi-halosaline is reported from n-butyraldehyde using iterative asymmetric allylation, nucleophilic substitution with an azide and ring-closing metathesis as the key reactions.
- Krishna, Palakodety Radha,Reddy, Bonepally Karunakar,Srinivas, Palabindela
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experimental part
p. 841 - 845
(2012/02/02)
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- Carbonyl allylation of aldehydes and ketones with allylic chlorides catalyzed by immobilization of palladium in MCM-41
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The heterogeneous carbonyl allylation of aldehydes and ketones with allylic chlorides was achieved in DMF using SnCl2 as reducing agent at 25-40 °C in the presence of a 3-(2-aminoethylamino)propyl-functionalized MCM-41-immobilized palladium(II) complex [MCM-41-2N-Pd(II)], yielding a variety of homoallylic alcohols in good to high yields. This heterogeneous palladium catalyst exhibited higher activity than (N-propylethylenediamine)PdCl 2 and can be recovered and recycled by a simple filtration of the reaction solution and used for at least 5 consecutive trials without any decreases in activity.
- Zhao, Hong,Peng, Jian,Xiao, Ruian,Hao, Wenyan,Cai, Ming-Zhong
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experimental part
p. 2030 - 2034
(2011/06/19)
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- Novel synthesis of stagonolide-F, putaminoxin and aspinolide-A
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Novel synthesis of putaminoxin, stagonolide-F and aspinolide-A have been achieved by utilizing (S) and (R)- malic acid. The key feature of the synthetic strategy includes Horner-Wittig olefination, double bond reduction and Steglich esterification. Olefinic acid for putaminoxin and stagonolide-F was prepared from (S)-malic acid whereas olefinic acid for aspinolide-A was prepared from (R)-malic acid and olefinic alcohols for putaminoxin, stagonolide-F and aspinolide-A were prepared by using Brown's asymmetric allylboration.
- Kamal, Ahmed,Reddy, Papagari Venkat,Balakrishna, Moku,Prabhakar, Singaraboina
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p. 143 - 149
(2013/01/10)
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- Formal synthesis of (-)-Neopeltolide featuring a highly stereoselective oxocarbenium formation/reduction sequence
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The formal synthesis of the unnatural (-)-neopeltolide core is discussed in detail. Efficient application of the Evans protocol for the synthesis of 1,3-syn-diols via an intramolecular hetero-Michael addition followed by reductive deprotection of the resulting benzylidene acetal allowed for swift access to the δ-lactone. Central to the synthetic approach is a tandem nucleophilic addition-diastereoselective axial reduction of an in situ generated oxocarbenium cation to assemble the β-C-glycoside moiety of the neopeltolide core.
- Martinez-Solorio, Dionicio,Jennings, Michael P.
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experimental part
p. 4095 - 4104
(2010/09/11)
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- Lanthanum trichloride: A simple and efficient catalyst for allylation of aldehydes with allyltributylstannane
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Aldehydes undergo smooth nucleophilic addition with allyltributyl-stannane in the presence of lanthanum trichloride to afford the corresponding homoallylic alcohols in excellent yields. All the reaction conditions were carried out in acetonitrile solvent at room temperature. In all the cases, the catalyst was used in a catalytic amount (10% mol). Copyright Taylor & Francis Group, LLC.
- Reddy, G. S. Satyanarayana,Sammaiah,Sharada
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experimental part
p. 3905 - 3911
(2009/12/25)
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- Synthesis of homoallylic alcohols by allylation of aldehydes and ketones catalysed by a mesoporous material (mcm-41)-supported cyano palladium complex
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A variety of homoallylic alcohols has been conveniently synthesised in good to high yields by the allylation of aldehydes and ketones with allylic chlorides catalysed by an MCM-41-supported cyano palladium complex in DMF using SnCl2 as reducing agent. This polymeric palladium complex can be recovered and reused with some loss of activity.
- Yao, Fang,Huang, Bin,Cai, Mingzhong
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experimental part
p. 366 - 369
(2009/12/25)
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- The first total synthesis of putaminoxin and determination of its absolute configuration
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Asymmetric synthesis of putaminoxin, a phytotoxic macrolide from the cultured dinoflagellate Amphidinium sp., has been accomplished. Absolute configuration of putaminoxin was concluded to be 1 from comparison of the NMR data and [α]D values of synthetic and natural putaminoxin.
- Sabitha, Gowravaram,Yadagiri,Swapna,Yadav
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scheme or table
p. 5417 - 5419
(2009/12/06)
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- Magnesium-cadmium chloride, a bimetallic catalyst system for the allylation of aldehydes with allyl bromide: An efficient protocol for the synthesis of homoallylic alcohols
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A simple and efficient procedure for the allylation of aldehydes has been developed using the magnesium-cadmium chloride reagent system. This bimetallic catalytic system works well in a tetrahydrofuran-water solvent medium. A variety of aldehydes undergo smooth nucleophilic addition with allyl bromide to afford the corresponding homoallylic alcohols in excellent yields. All the reactions were performed at room temperature. Georg Thieme Verlag Stuttgart.
- Venkat Narsaiah,Ramesh Reddy,Gopala Rao,Vijay Kumar,Prakasham,Subba Reddy, Basi V.,Yadav, Jhillu S.
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experimental part
p. 3461 - 3464
(2009/05/26)
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- Pd-catalyzed carboetherification ofβ,γ-unsaturated oximes: A novel approach to δ2-lsoxazolines
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A novel route to the synthesis of δ2-isoxazoline derivatives is described. Reaction of β,γ-unsaturated oximes with aryl bromides via palladium-catalyzed carboetherification affords 3,5-disubstituted δ2-isoxazollnes in good yields. The use of Xantphos as ligand Is crucial for the transformation. The carboetherification products can be further converted to β-hydroxy ketones in the presence of Fe powder and NH4CI.
- Jiang, Dahong,Peng, Jinsong,Chen, Yuanwei
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supporting information; experimental part
p. 1695 - 1698
(2009/04/12)
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- Formal synthesis of herbarumin III
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An enantioselective synthesis of herbarumin III is described employing Jacobsen's hydrolytic kinetic resolution and Sharpless asymmetric dihydroxylation as the key steps.
- Gupta, Priti,Kumar, Pradeep
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p. 1688 - 1692
(2008/02/11)
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- Bismuth triflate catalyzed allylation of aldehydes with allylstannane under microwave assistance
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In the presence of a catalytic amount of bismuth triflate and under microwave irradiation, mixtures of aldehyde and allyl-stannane afforded smoothly the corresponding homoallylic alcohol. A wide variety of aldehydes were treated under these conditions. The reactions proceeded rapidly and afforded smoothly the corresponding homoallylic alcohol in good to very good yields using catalytic amounts of Bi(OTf)3·4H2O (0.5mol-%) and under microwave irradiation for a short time. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Ollevier, Thierry,Li, Zhiya
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p. 5665 - 5668
(2008/09/17)
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- SnCl2-mediated carbonyl allylation of aldehydes and ketones in ionic liquid
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In ionic liquid [bmim]BF4, SnCl2·2H 2O acts as an inexpensive and efficient metal salt for carbonyl allylation. By applying ionic liquid, some previously reported serious operational problems associated with the SnCl2-mediated allylation reaction are avoided. Furthermore, ketones, which are less reactive than aldehydes, can also be allylated in high yields with this system.
- Tang, Long,Ding, Li,Chang, Wei-Xing,Li, Jing
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p. 303 - 306
(2007/10/03)
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- Enantioselective allylation of aldehydes promoted by chiral sulfur reagents
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The addition of allylzinc bromide to aldehydes was studied with different chiral sulfur compounds acting as a catalyst. Yield differences and enantiomeric excesses were observed.
- Melo, Rosanne P.A.,Vale, Juliana A.,Zeni, Gilson,Menezes, Paulo H.
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p. 1829 - 1831
(2007/10/03)
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- A short enantioselective total synthesis of the phytotoxic lactone herbarumin III
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The synthesis of the phytotoxic lactone herbarumin III in 11 % overall yield by fermentation of broth and mycelium of the fungus Phoma herbarum is described. Keck's asymmetric allylation and Sharpless epoxidation are applied to build the key fragment of the compound. A ring closing metathesis and esterification with 5-hexanoic acid are used to obtain the compound. The synthesis is initiated by the application of the catalytic asymmetric allyl protocol. Chain elongation of the aldehyde through Wittig olefination with triphenyl carbethoxymethyl phosphonium chloride supported on alumina under microwave irradiation provided the α, β - unsaturated ester as the major product. The ring opening metathesis with Grubbs second-generation catalyst gave Herbarumin III as a clear oil. The complete procedure involved the synthesis of the compound from n-butanal in 11 % overall yield.
- Boruwa, Joshodeep,Gogoi, Naminita,Barua, Nabin C.
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p. 3521 - 3525
(2008/09/16)
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- Asymmetric allyl- and crotylboration with the robust, versatile, and recyclable 10-TMS-9-borabicyclo[3.3.2]decanes
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The remarkable versatility and selectivity of the 10-(trimethylsilyl)-9- borabicyclo[3.3.2]decanes (10-TMS-9-BBDs) in the allyl- and crotylboration of representative aldehydes are reported. The new reagents are prepared through air-stable crystalline pseudoephedrine borinic ester complexes of the 10-TMS-9-BBDs (4), which are available in 63% overall yield from B-MeO-9-BBN through a simple two-step procedure. These complexes 4 are directly converted to the corresponding B-allyl-10-TMS-9-BBDs (1) with allylmagnesium bromide, which either can be isolated (98%) or used in situ for the allylations. The remarkable enantioselectivity (96 to ≥99% ee) of these reagents in the rapid (3 h), asymmetric allylboration process at -78 °C is only slightly diminished when it is conducted at 25 °C, a phenomenon attributable to its rigid bicyclic structure. In addition to providing the homoallylic alcohols 6 efficiently (68-80%), the procedure also permits the efficient recovery of 4 (68-84%) for the direct regeneration of 1. Alternatively, an oxidative workup procedure can be used for the preparation of 6. The reagent gives predictable stereochemistry and exhibits an extremely high level of reagent control in the allylboration of D-glyceraldehyde acetonide. A simple and efficient procedure has been developed for the preparation of all four geometric and enantiomeric isomers of the B-crotyl-10-TMS-9-BBDs (10) from optically pure enantiomers of B-MeO-10-TMS-9-BBD (3). These reagents 10 also add rapidly (3 h) and efficiently to representative aldehydes at -78 °C, providing ready access to all four of the possible stereoisomers of the β-methyl homoallylic alcohols 12-15 (69-92%) in high dr (≥98:2) and ee (94-99%).
- Burgos, Carlos H.,Canales, Eda,Matos, Karl,Soderquist, John A.
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p. 8044 - 8049
(2007/10/03)
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- Total synthesis of (+)-trans-195A
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(Chemical Equation Presented) The first enantioselective synthesis of (+)-trans-195A is described. The structure has been constructed by ring-rearrangement metathesis (RRM) and zirconium-mediated Negishi-coupling, used for the first time to prepare 6,6-membered heterocycles, as key steps. By comparison of the synthesized material with the isolated natural product, the absolute configuration of natural trans-195A was determined to be (2R,4aS,5R,8aS)-(-).
- Holub, Nicole,Neidhoefer, Juergen,Blechert, Siegfried
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p. 1227 - 1229
(2007/10/03)
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- A highly efficient and practical new allylboronate tartramide for the asymmetric allylboration of achiral aldehydes
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Chiral homoallylic alcohols can be prepared from aldehydes upon reaction with two optically pure allylboronate tartramides. The enantiomeric excess is 10-15% higher for the allylation of benzaldehyde when using N,N'-dibenzyl-tartramide auxiliary 5b than when using N,N'-diphenyl-tartramide (5a). 2-Allyl-N,N'-dibenzyl-1,3,2-dioxaborolane-4,5-dicarbamide (2b) affords homoallylic alcohols with 90-99% ee upon reaction with some representative aldehydes. The derivatised chiral auxiliaries can be recovered by simple recrystallization, in 85% yield, without any loss of specific rotation. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
- Chen, Wansuo,Liu, Yanzhu,Chen, Zhirong
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p. 1665 - 1668
(2007/10/03)
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- SnCl2-mediated carbonyl allylation in fully aqueous media
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Systematic studies were performed on SnCl2-mediated carbonyl allylation reaction between aldehydes and allyl halides in fully aqueous media. Totally three valuable reaction systems were discovered, which were SnCl 2/CuCl2, SnCl2/TiCl3, and SnCl 2/PdCl2. They all provided good to excellent yields in the allylation of aliphatic and aromatic aldehydes under very mild and convenient conditions. SnCl2, by itself, was also found to be effective for the allylation reaction when allyl bromide was employed. However, the SnCl 2-only reaction could only tolerate very small amount of water as the solvent. The SnCl2/CuCl2, SnCl2/TiCl 3, and SnCl2/PdCl2-mediated reactions exhibited good regioselectivity favoring the γ-adduct when cinnamyl halides were employed as the allylation reagent. The same reactions with cinnamyl halides also showed good diastereoselectivity favoring the anti-product. Mechanistic studies using proton NMR techniques suggested that the additive (i.e., CuCl 2, TiCl3, PdCl2) could accelerate the formation of allyltin intermediate, but this step was shown not to be the most important for the allylation. Thus we proposed that the Lewis acid catalysis effect exerted by the additive was the main reason for the observed reactivity enhancement.
- Tan, Xiang-Hui,Hou, Yong-Quan,Huang, Chao,Liu, Lei,Guo, Qing-Xiang
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p. 6129 - 6136
(2007/10/03)
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- SnCl2/PdCl2-mediated aldehyde allylation in fully aqueous media
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Catalyzed by PdCl2, SnCl2 can efficiently mediate the allylation of various aldehydes with allyl chloride or bromide, but not with allyl alcohol, in fully aqueous media. The yield of the reaction is very high (90-100%), and the reaction is operationally simple, environmental benign and easy to scale up.
- Tan, Xiang-Hui,Hou, Yong-Quan,Shen, Bo,Liu, Lei,Guo, Qing-Xiang
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p. 5525 - 5528
(2007/10/03)
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- Novel ultrasonication-assisted carbonyl allylation mediated by SnCl 2 in water
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Under ultrasonication, it was found that SnCl2 could efficiently mediate the aqueous Barbier reactions between carbonyl compounds and allyl bromide to give the corresponding homoallylic alcohols in high yields without using any Lewis acid catalyst.
- Wang, Jun,Yuan, Gu,Dong, Chang-Qing
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p. 286 - 287
(2007/10/03)
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- Diastereoselective synthesis of 2,5-disubstituted decahydroquinolines via ring-rearrangement metathesis and zirconium-mediated cyclization
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A diastereoselective approach to 2,5-substituted decahydroquinolines by zirconium-mediated cyclization of unsaturated α,α′- disubstituted piperidines II is described. The required piperidines could be obtained from secondary sulfonamides III via ruthenium-catalyzed ring-rearrangement metathesis (RRM) in high yields. Racemic trans-195A and 2-epi-trans-195A were synthesized in 8 steps starting with butyraldehyde and cyclohex-2-enol.
- Neidhoefer, Juergen,Blechert, Siegfried
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p. 3047 - 3054
(2007/10/03)
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- Carbonyl allylation of aldehydes catalyzed by a silica-supported poly-γ-diphenylarsinopropylsiloxane palladium(0) complex
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A silica-supported poly-γ-diphenylarsinopropylsiloxane palladium (0) complex has been prepared from γ-chloropropyltriethoxysilane via immobilization on fumed silica, followed by reacting with potassium diphenylarsenide and palladium chloride, and then the reduction with hydrazine hydrate. The palladium(0) complex has been found to catalyze the allylation of aldehydes via the formation of π-allylpalladium complexes, using allylic chlorides as allylating agent and SnCl2 as reducing agent. This polymeric palladium complex can be recovered and reused.
- Cai, Mingzhong,Huang, Yizheng,Zhao, Hong,Zhang, Rongli
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p. 2436 - 2440
(2007/10/03)
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- Gal3 catalysed nucleophilic addition of allyltrimethylsilane to aldehydes
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In dichloromethane, the nucleophilic addition of allyltrimethylsilane to aldehydes to give the corresponding homoallyl alcohols in good to excellent yields was catalysed effectively by gallium triiodide which was generated in situ by the reaction of gallium metal and iodine.
- Sun, Peipei,Xian, Yufang,Xiao, Yaping
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p. 216 - 217
(2007/10/03)
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- Carbon-carbon bond formation using bismuth in a water medium
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In the presence of bismuth and ammonium chloride, allyl halides were found to react with aldehydes in a water medium at room temperature to give the corresponding homoallylic alcohols.
- Miyamoto, Hisakazu,Daikawa, Naoki,Tanaka, Koichi
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p. 6963 - 6964
(2007/10/03)
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- The preparation of nonracemic secondary α-(carbamoyloxy)alkylzinc and copper reagents. A versatile approach to enantioenriched alcohols
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(matrix presented) Chiral α-(carbamoyloxy)alkyllithium reagents, prepared using Hoppe's sBuLi/(-)-sparteine methodology, were transmetalated with ZnCl2. Further transmetalation with CuCN with overall retention of configuration gave chiral species that reacted with various electrophiles to give enantiomerically pure alcohols after deprotection. A short, highly efficient synthesis of an industrially relevant pheromone, japonilure, illustrates the value of the methodology.
- Papillon, Julien P. N.,Taylor, Richard J. K.
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p. 119 - 122
(2007/10/03)
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- Sc(OTf)3, an efficient catalyst for addition of allyltrimethysilane to aldehydes: Chemoselective addition to aldehydes in presence of ketone and in situ acylation (3-component coupling)
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Scandium triflate (2-10 mol%) have been found to be a highly efficient catalyst for the addition of allyltrimethylsilane to both activated aromatic and aliphatic aldehydes. However, deactivated (electron rich) aromatic aldehydes gave double allylated products instead. Using a stoichiometric amount of Ac2O in the allylation reaction led directly to homoallylic acetates [in situ acylation catalysed by Sc(OTf)3] and for the first time gave high yields of adducts with moderately electron rich aromatic aldehydes.
- Aggarwal, Varinder K.,Vennall, Graham P.
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p. 1822 - 1826
(2007/10/03)
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- A new type of allyl- And prop-2-ynyl-manganese species: Generation and reactions with electrophiles
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Tetrabutylmanganese ate complex 'Bu4MnLi2' reacts with allylic and prop-2-ynylic bromides to generate the corresponding allyl- and prop-2-ynyl-manganese species which further react with electrophiles such as aldehydes, ketones, epoxide and chlorosilanes to afford the corresponding allylated and prop-2-ynylated and/or allenylated products in high yields.
- Hojo, Makoto,Harada, Hajime,Ito, Hajime,Hosomi, Akira
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p. 2077 - 2078
(2007/10/03)
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- Tandem asymmetric allylboration-alkene metathesis: A novel strategy for the synthesis of trans-disubstituted homoallylic alcohols
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Tandem use of Brown's asymmetric allylboration technology and crossed-alkene metathesis provides exclusively trans-disubstituted homoallylic alcohols in good yields.
- Barrett, Anthony G. M.,Beall, Jennifer C.,Gibson, Vernon C.,Giles, Matthew R.,Walker, Gary L. P.
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p. 2229 - 2230
(2007/10/03)
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- Preparation of Monosilyl Acetals from Esters via iBu2AlH Reduction and Trapping with N-(Trimethylsilyl)imidazole. Addition of Allyltrimethylsilane To Yield Homoallylic Alcohols or Ethers
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Alkyl esters were reduced with iBu2AlH or a 1:1 mixture of iBu2AlH and iBu3Al (iBu2AlH*iBu3Al or iBu5Al2H), followed by trapping of the resulting tetrahedral intermediate with TMS-imidazole to produce monosilyl acetals.Reaction of the mixed acetals with allyltrimethylsilane in the presence of Lewis acids (Hosomi-Sakurai reaction) generated homoallylic alcohols or ethers selectively, depending on the substitution of the monosilyl acetal.TMS methoxy acetals (MeO-CH-OTMS) and TMS ethoxy acetals bearing additional complexing groups such as MeO- or Ph2C=N- provided alcohols with 1.5:1 - 9:1 threoselectivity, while simple TMS ethoxy acetals provided only ethyl ethers as products.The monosilyl acetal configuration was easily epimerized or racemized, and the configuration of the Hosomi-Sakurai product was apparently independent of the initial monosilyl acetal reactant configuration.
- Sames, Dalibor,Liu, Yunqi,DeYoung, Lynn,Polt, Robin
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p. 2153 - 2159
(2007/10/02)
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- A highly efficient addition of allylic bromides to carbonyl compounds promoted by Cp2TiCI2(cat.)/Zn system
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Aldehydes or ketones reacted with allylic bromides in the presence of Cp2TiCl2(cat.)/Zn system at room temperature to give homo-allylic alcohols in high yields.
- Ding, Yu,Zhao, Gang
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p. 8117 - 8118
(2007/10/02)
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- Chiral Synthesis via Organoboranes. 27. Remarkably Rapid and Exceptionally Enantioselective (Approaching 100percent ee) Allylboration of Representative Aldehydes at -100 deg C under New Salt-Free Conditions
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In the absence of magnesium salts (from the synthesis of the reagents), our chiral B-allylditerpenylborane reagents (Ter2*BCH2CH=CH2), 1-3) react with representative aldehydes (RCHO, R=Me, n-Pr, i-Pr, t-Bu, vinyl, and Ph) practically instantaneously at -100 deg C to give homoallylic alcohols (R*CH(OH)CH=CH2) with optical purities approaching 100percent ee.The exceptional reaction rate achieved at -100 deg C indicates that these allylborations are among the fastest reactions presently known to the organic chemist.The short reaction time adopted (dIpc2BAll, d1) give homoallylic alcohols of >/= 98percent ee and B-allylbis(2-isocaranyl)borane (2-dIcr2BAll, 3) provides alcohols of >/= 99percent ee.The enantioselectivities (>/= 99percent ee) achieved in allylboration by the reagent 3 are essentially perfect, making this one of the most stereoselective reactions currently known in organic chemistry.
- Racherla, Uday S.,Brown, Herbert C.
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p. 401 - 405
(2007/10/02)
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- Chiral synthesis via organoboranes. 24. B-allylbis(2-isocaranyl)borane as a superior reagent for the asymmetric allylboration of aldehydes
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Hydroboration of (+)-2-carene, readily available via the base-induced isomerization of (+)-3-carene, provides bis(2-isocaranyl)borane, which can be readily transformed into B-allylbis(2-isocaranyl)borane (2-dICr2BAll). This new reagent undergoes asymmetric allylboration with a variety of aldehydes and affords the corresponding homoallylic alcohols in 94-99% ee. The enantioselectivities realized with this reagent are significantly higher than those realized with the previously explored reagents, B-allyldiisopinocampheylborane (dIpc2Ball) and B-allylbis(4-isocaranyl)borane (4-dIcr2BAll).
- Brown, Herbert C.,Randad, Ramnarayan S.,Bhat, Krishna S.,Zaidlewicz, Marek,Racherla, Uday S.
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p. 2389 - 2392
(2007/10/02)
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