Lewis base-catalyzed three-component Strecker reaction on water. An efficient manifold for the direct α-cyanoamination of ketones and aldehydes
作者:Fabio Cruz-Acosta、Alicia Santos-Expósito、Pedro de Armas、Fernando García-Tellado
DOI:10.1039/b914151k
日期:——
The first three-component organocatalyzed Strecker reaction operating on water has been developed. The manifold utilizes ketones (aldehydes) as the starting carbonyl component, aniline as the primary amine, acetyl cyanide as the cyanide source and N,N-dimethylcyclohexylamine as the catalyst.
Additions of structurally diverse α-ketonitriles to aromatic and aliphatic prochiral aldehydes yielding highly enantioenriched acylated cyanohydrins were achieved using a combination of a titanium salen dimer and an achiral or chiral Lewis base. In most cases high yields and high enantioselectivities were observed. The ee was moderate in the initial part of the reaction but increased over time. This
A palladium‐catalyzed tandem reaction of cyanomethyl benzoates with arylboronic acids has been achieved. Substitution at the 2‐position of cyanomethyl benzoates was found to be crucial for the selective synthesis of oxazoles and isocoumarins. Cyanomethyl benzoates afforded 2,4‐diaryloxazoles as products, while 2‐benzoyl‐substituted cyanomethyl benzoates delivered 3‐benzoyl‐4‐aryl‐isocoumarins selectively
Vinylogous urethanes in alkaloid synthesis: formal syntheses of Elaeocarpus alkaloids
作者:Arthur S. Howard、Graeme C. Gerrans、Clive A. Meerholz
DOI:10.1016/s0040-4039(00)74580-1
日期:1980.1
dehydroindolizidine has been prepared from the exocyclic vinylogous urethane via an acylative ring closure. The specific formation of the enolate required for further elaboration to Elaeocarpusalkaloid precursors has been achieved by making use of the vinylogous amide .
A minorenantiomerrecycling one‐pot procedure employing two reinforcing chiral catalysts has been developed. Continuous regeneration of the achiral starting material is effected via selective enzyme‐catalyzed hydrolysis of the minor product enantiomer from Lewis acid–Lewis base catalyzed addition of acyl cyanides to prochiral aldehydes in a two‐phase solvent system. The process provides O‐acylated
已开发出一种使用两种增强手性催化剂的较小对映体回收一锅法。非手性原料的连续再生是通过路易斯酸-刘易斯碱在两相溶剂体系中将酰基氰化物加成到手性醛中的次要产物对映异构体的选择性酶催化水解来实现的。该方法提供的O-酰化氰醇接近完美的对映选择性,高于直接法获得的对映选择性,并且收率很高。(S,S)-salen Ti Lewis酸和南极假丝酵母脂肪酶B的组合可提供具有R绝对构型的产物,而相反的对映异构体可从(R,R)-salen Ti复合物和皱纹念珠菌脂肪酶。