Direct organocatalytic asymmetric alpha-chlorination of aldehydes.

阅读量：

作者：

N Halland，A Braunton，S Bachmann，M Marigo，Karl Anker Joergensen

展开

摘要：

The direct organocatalytic enantioselective alpha-chlorination of aldehydes has been developed. The reaction proceeds for a series of different aldehydes with NCS as the chlorine source using easily available catalysts such as l-proline amide and (2R,5R)-diphenylpyrrolidine. The alpha-chloro aldehydes are obtained in up to 99% yield and up to 95% ee. The synthetic utility of the enantioselective alpha-chlorination of aldehydes is demonstrated by transformation of the alpha-chloro aldehydes to the corresponding alpha-chloro alcohols (>90% yield) by standard reduction and further transformation to both a terminal epoxide and amino alcohol, both obtained without loss of optical purity. Oxidation of the alpha-chloro aldehydes followed by esterification gave optically active alpha-chloro esters without loss of optical purity. It is demonstrated that these optically active alpha-chloro esters can be converted into nonproteinogenic amino acids in overall high yields, maintaining the enantiomeric excess obtained in the catalytic enantioselective alpha-chlorination step.

展开

关键词：

diastereoselective syntheses, enantioselective syntheses (incl. cis/trans‐isomerism) halogenation halogen compounds (benzene compounds) halogen compounds (acyclic compounds)

DOI：

10.1002/chin.200433024

被引量：

781

年份：

2004