STERIC CONTROL OF THE ASYMMETRIC SYNTHESIS OF N-SUBSTITUTED 2-METHYL-4-PIPERIDONES

Article abstract of DOI:10.1007/BF00842959

Transmission of the iodomethylate of 1,2-dimethyl-4-piperidone by (S)-sec-butylamine gives 1-(S-sec-butyl)-2S-methyl-4-piperidone in 33percent optical yield while transamination by (S)-1-methyl-2-phenylethylamine gives a 1:1 diastereomeric mixture of 1-(1-methyl-2-phenylethyl)-2-methyl-4-piperidone.The decrease in the optical yield is related to the facile opening of the piperidone ring at the C-N bond with subsequent recyclization.The 13C NMR data indicate that all the diastereomers of the 4-piperidones obtained are in the chair conformation with predominantly equatorial orientation of the methyl group at C₍₂₎.The chi ral optical properties were studied and the absolution configurations of the 4-piperidones were established.