Lipase catalyzed resolution of the quaternary stereogenic center in ketone-derived benzo-fused cyclic cyanohydrins
摘要:
The enantioselective preparation of both enantiomers of the benzo-fused cyanohydrin derived from alpha-tetralone via lipase catalyzed processes is described. The (S)-enantiomer has been obtained as the remaining substrate in the CAL-A catalyzed aminolysis of the methoxyacetylated derivative, using a structurally related amine as the nucleophile. The (R)-enantiomer has been obtained as the product of CAL-A or PSL-C catalyzed hydrolysis of the methoxyacetylated derivative in organic solvents. The resolutions of several structural analogs of this cyanohydrin have been also tested under similar conditions. (C) 2011 Elsevier Ltd. All rights reserved.
Me<sub>2</sub>(CH<sub>2</sub>Cl)SiCN: Bifunctional Cyanating Reagent for the Synthesis of Tertiary Alcohols with a Chloromethyl Ketone Moiety via Ketone Cyanosilylation
作者:Xing-Ping Zeng、Jian Zhou
DOI:10.1021/jacs.6b05601
日期:2016.7.20
We report a novel bifunctional cyanating reagent, Me2(CH2Cl)SiCN, which paves the way to a one-pot sequential synthesis of tertiary alcohols featuring a chloromethyl ketone moiety via enantioselectiveketonecyanosilylation. This method contributes to gram-scale enantioselective total synthesis of the aggregation pheromone of the Colorado potato beetle, (S)-CPB.
the bifunctionalcatalyst 1 afforded the improved catalyst 2, which promoted the cyanosilylation of ketones with higher enantioselectivity as well as with improved catalyst turn-over with a factor of up to 10. Thus, chiral quaternary α-hydroxynitriles were obtained with excellent ee (up to 94% ee) using 1 mol% of 2 in the case of aryl ketones and 2.5 mol% of 2 in the case of aliphatic ketones.
Effective Activation of the Chiral Salen/Ti(OiPr)4 Catalyst with Achiral PhenolicN-Oxides as Additives in the Enantioselective Cyanosilylation of Ketones
the asymmetric cyanosilylation of ketones. By using 10 mol % of chiral salen-titanium(IV) complex in combination with 1 mol% achiral phenolic N-oxide as an additive, aromatic, aliphatic and heterocyclic ketones have been converted into the corresponding cyanohydrin trimethylsilyl ethers in 58-96% yields with 56-82% ee. Several factors concerning the reactivity and enantioselectivity have been discussed
An efficient and optically active, bifunctional tetraaza ligand (2S)-N-(1R,2R)-2-[(S)-pyrrolidine-2-carboxamido]-1,2-diphenylethyl}pyrrolidine-2-carboxamide has been developed for the addition of trimethylsilyl cyanide (TMSCN) to ketones. The bifunctionalcatalyst system based on a monometallic titanium complex was found to be a highly enantioselectivecatalyst to provide O-TMS cyanohydrins with up