Direct Organocatalytic Asymmetric α-Chlorination of Aldehydes Nis Halland Alan Braunton Stephan Bachmann Mauro Marigo Karl Anker Jørgensen 10.1021/ja049231m.s001 https://acs.figshare.com/articles/dataset/Direct_Organocatalytic_Asymmetric_Chlorination_of_Aldehydes/3342214 The direct organocatalytic enantioselective α-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 (2<i>R</i>,5<i>R</i>)-diphenylpyrrolidine. The α-chloro aldehydes are obtained in up to 99% yield and up to 95% ee. The synthetic utility of the enantioselective α-chlorination of aldehydes is demonstrated by transformation of the α-chloro aldehydes to the corresponding α-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 α-chloro aldehydes followed by esterification gave optically active α-chloro esters without loss of optical purity. It is demonstrated that these optically active α-chloro esters can be converted into nonproteinogenic amino acids in overall high yields, maintaining the enantiomeric excess obtained in the catalytic enantioselective α-chlorination step. 2004-04-21 00:00:00 chlorine source enantioselective aldehyde reaction proceeds chlorination terminal epoxide NCS chloro