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Enantioselective Organocatalytic Reduction of β‐Trifluoromethyl Nitroalkenes: An Efficient Strategy for the Synthesis of Chiral β‐Trifluoromethyl Amines 下载免费PDF全文
Elisabetta Massolo Prof. Maurizio Benaglia Manuel Orlandi Dr. Sergio Rossi Giuseppe Celentano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(9):3589-3595
An efficient organocatalytic stereoselective reduction of β‐trifluoromethyl‐substituted nitroalkenes, mediated by 3,5‐dicarboxylic ester‐dihydropyridines (Hantzsch ester type), has been successfully developed. A multifunctional thiourea‐based (S)‐valine derivative was found to be the catalyst of choice, promoting the reaction in up to 97 % ee. The methodology has been applied to a wide variety of substrates, leading to the formation of differently substituted precursors of enantiomerically enriched β‐trifluoromethyl amines. The mechanism of the reaction and the mode of action of the metal‐free catalytic species were computationally investigated; on the basis of DFT transition‐state (TS) analysis, a model of stereoselection was also proposed. 相似文献
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Highly Enantioselective [3+2] Cycloaddition of Vinylcyclopropane with Nitroalkenes Catalyzed by Palladium(0) with a Chiral Bis(tert‐amine) Ligand 下载免费PDF全文
Feng Wei Chuan‐Li Ren Prof. Dr. Dong Wang Prof. Dr. Li Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2335-2338
An enantioselective [3+2] cycloaddition of vinyl cyclopropane derived from 1,3‐indanedione with nitroalkenes catalyzed by palladium(0) with a chiral bis(tert‐amine) ligand was developed in high yields with good diastereoselectivities and excellent enantioselectivities. The resulting bis(tert‐amine)–palladium complex proved to be a highly efficient catalyst for this cycloaddition. 相似文献
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Dr. Ramulu Akula Dr. Robert Doran Prof. Patrick J. Guiry 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(29):9938-9942
A highly enantioselective Pd‐catalysed decarboxylative asymmetric allylic alkylation of cyclopentanone derived α‐aryl‐β‐keto esters employing the (R,R)‐ANDEN‐phenyl Trost ligand has been developed. The product (S)‐α‐allyl‐α‐arylcyclopentanones were obtained in excellent yields and enantioselectivities (up to >99.9 % ee). This represents one of the most highly enantioselective formations of an all‐carbon quaternary stereogenic center reported to date. This reaction was demonstrated on a 4.0 mmol scale without any deterioration of enantioselectivity and was exploited as the key enantioselective transformation in an asymmetric formal synthesis of the natural product (+)‐tanikolide. 相似文献
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Jia‐Qi Li Xu Quan Prof. Dr. Pher G. Andersson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(34):10609-10616
α,β‐Unsaturated esters have been employed as substrates in iridium‐catalyzed asymmetric hydrogenation. Full conversions and good to excellent enantioselectivities (up to 99 % ee) were obtained for a broad range of substrates with both aromatic‐ and aliphatic substituents on the prochiral carbon. The hydrogenated products are highly useful as building blocks in the synthesis of a variety of natural products and pharmaceuticals. 相似文献
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Highly Enantioselective Catalytic Asymmetric [2+2] Cycloadditions of Cyclic α‐Alkylidene β‐Oxo Imides with Ynamides 下载免费PDF全文
Kazuaki Enomoto Harufumi Oyama Prof. Dr. Masahisa Nakada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(7):2798-2802
Highly enantioselective catalytic asymmetric [2+2] cycloadditions of cyclic α‐alkylidene β‐oxo imides with ynamides are described. The high reactivity of the cyclic α‐alkylidene β‐oxo imide allows the [2+2] cycloadditions of a hindered substrate with unreactive ynamides at low temperature. The X‐ray crystallographic analysis of the product suggests that the enantioselectivity of the [2+2] cycloaddition can be well explained by the chelate model comprising the intramolecular hydrogen bond, wherein the cyclic α‐alkylidene β‐oxo imide coordinates with CuII through the two imide carbonyls. The imide group in the product can be transformed to amide, nitrile, and ester groups; moreover, it is removable. 相似文献
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《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(1):63-71
New asymmetric conjugate reduction of β,β‐disubstituted α,β‐unsaturated ketones and esters was accomplished with alkoxylhydrosilanes in the presence of chiral rhodium(2,6‐bisoxazolinylphenyl) complexes in high yields and high enantioselectivity. (E)‐4‐Phenyl‐3‐penten‐2‐one and (E)‐4‐phenyl‐4‐isopropyl‐3‐penten‐2‐one were readily reduced at 60 °C in 95 % ee and 98 % ee, respectively, by 1 mol % of catalyst loading. (EtO)2MeSiH proved to be the best hydrogen donor of choice. tert‐Butyl (E)‐β‐methylcinnamate and β‐isopropylcinnamate could also be reduced to the corresponding dihydrocinnamate derivatives up to 98 % ee. 相似文献
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Highly Enantioselective Aza‐Michael Reaction between Alkyl Amines and β‐Trifluoromethyl β‐Aryl Nitroolefins 下载免费PDF全文
Prof. Dr. Yong Huang 《Angewandte Chemie (International ed. in English)》2015,54(51):15414-15418
The aza‐Michael addition reaction is a vital transformation for the synthesis of functionalized chiral amines. Despite intensive research, enantioselective aza‐Michael reactions with alkyl amines as the nitrogen donor have not been successful. We report the use of chiral N‐heterocyclic carbenes (NHCs) as noncovalent organocatalysts to promote a highly selective aza‐Michael reaction between primary alkyl amines and β‐trifluoromethyl β‐aryl nitroolefins. In contrast to classical conjugate‐addition reactions, a strategy of HOMO‐raising activation was used. Chiral trifluoromethylated amines were synthesized in high yield (up to 99 %) with excellent enantioselectivity (up to 98 % ee). 相似文献
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Highly Diastereo‐ and Enantioselective Palladium‐Catalyzed [3+2] Cycloaddition of Vinyl Aziridines and α,β‐Unsaturated Ketones 下载免费PDF全文
Chao‐Fan Xu Bao‐Hui Zheng Jia‐Jia Suo Dr. Chang‐Hua Ding Prof. Dr. Xue‐Long Hou 《Angewandte Chemie (International ed. in English)》2015,54(5):1604-1607
A palladium‐catalyzed asymmetric [3+2] cycloaddition reaction of vinylaziridines with α,β‐unsaturated ketones, wherein the alkenes have a single activator, is realized in high diastereo‐ and enantioselectivity, thus affording 3,4‐disubstituted pyrrolidines in high yields with excellent ee values. The introduction of a methyl group at C1 of the vinyl group the vinylaziridines greatly improves the stereochemistry of the reaction. A plausible transition state is proposed. 相似文献
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Zhen Wang Donghui Chen Zhigang Yang Sha Bai Xiaohua Liu Dr. Lili Lin Dr. Xiaoming Feng Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(33):10130-10136
Highly enantioselective Michael addition of 1,3‐dicarbonyl compounds and nitromethane to 4‐oxo‐4‐arylbutenoates catalyzed by N,N′‐dioxide–Sc(OTf)3 complexes has been developed. Using 0.5–2 mol % catalyst loading, various α‐stereogenic esters were obtained regioselectively with excellent yields (up to 97 %) and enantioselectivities (up to >99 % ee). Moreover, the reaction performed well under nearly solvent‐free conditions. The products with functional groups are ready for further transformation, which showed the potential value of the catalytic approach. According to the experimental results and previous reports, a plausible working model has been proposed to explain the origin of the activation and the asymmetric induction. 相似文献
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Dr. Cheng‐Kui Pei Yu Jiang Yin Wei Prof. Dr. Min Shi 《Angewandte Chemie (International ed. in English)》2012,51(45):11328-11332