Enantioselective addition of dimethylzinc to aldehydes:: assessment of optimal N,N-substitution for 2-dialkylamino-1,1,2-triphenylethanol ligands

A general methodology for the synthesis of 2-dialkylamino-1,1,2-triphenylethanol has been developed. Novel ligands 3, 4, and 5, bearing flexible alkyl chains on nitrogen have been synthesized by epoxide-ring opening of the encumbered (S)-triphenyloxirane. These ligands along with 2-piperidino-1,1,2-triphenyl ethanol 1 have been tested in the addition of dimethylzinc to aldehydes. This allowed for the assessment of the structural features that favor the catalytic activity and selectivity of the ligands with respect to nitrogen substitution. (C) 2004 Elsevier Ltd. All rights reserved.