Metal or ammonium alginates as Lewis base catalysts for the 1,2-addition of silyl nucleophiles to carbonyl compounds
摘要:
Several metal (Na+, Ca2+) or ammonium (n-Bu4N+) derivatives of alginic acid, an abundant bio-polymer obtained from the cell walls of brown algae, were synthesized. Their potential to act as organocatalysts to catalyze the 1,2-addition of various silyl derivatives to carbonyl compounds was evaluated for the first time. Ammonium alginate 1h is able to promote the reaction in modest to good isolated yields (up to 98%) affording access to a large range of substrates (beta-cyano alcohols or ester, beta-substituted methylacrylate or acrylonitrile, and cyanohydrin) by using only 5 mol % of catalyst. (C) 2012 Elsevier Ltd. All rights reserved.
An aldol-type reaction of organonitriles with aldehydes was catalyzed by a RhI(OR) species underambientconditions, and the reaction displayed a broad substrate scope with respect to both organonitrile and aldehyde components.
Rhodium to the rescue: The formal aldol products of carboxamides (CONH2) were obtained by using a RhI(OR) (R=H, Me) catalyst under essentially neutral pH and ambient conditions. This novel aldol strategy is based on the catalytic aldol‐type reaction of nitriles, followed by hydration of the nitrile functionality (R1=aromatic or aliphatic, R2 and R3=H or alkyl; see scheme).
Efficient Lipase-Catalyzed Kinetic Resolution and Dynamic Kinetic Resolution of β-Hydroxy Nitriles. Correction of Absolute Configuration and Transformation to Chiral β-Hydroxy Acids and γ-Amino Alcohols
Chemoenzymatic dynamickineticresolution of β-hydroxy nitriles 1 has been carried out using Candida antarctica lipase B and a ruthenium catalyst. The use of a hydrogen source to depress ketone formation in the dynamickineticresolution yields the corresponding acetates 2 in good yield and high enantioselectivity. It is shown that the ruthenium catalyst and the enzyme can be recycled when used in
Process for preparing 3-heteroaryl-3-hydroxypropanoic acid derivatives
申请人:——
公开号:US20040181058A1
公开(公告)日:2004-09-16
The invention relates to a process for preparing enantiomer-enriched 3-heteroaryl-3-hydroxypropanoic acid derivatives and 3-heteroaryl-1-aminopropan-3-ols, and to their use.