Configurations in unsymmetrically N-methyl-N-substituted 2-phenylacetamides

Abstract

The syntheses of a various N-methyl-N-substituted 2-phenylacetamides of the general formula PhCH 2 CON(CH 3 )R, wherein, R is ethyl, n-propyl, isopropyl and t-butyl group, were performed. The 1 H n.m.r. spectra of these unsymetrically N,N-disubstituted amides have been studied and the peaks have been assigned in each case to the two possible conformational isomers, arising from the lack of free rotation about the C(O)N bond. Although the cis form predominates, the percentage of cis isomer increases as the other nitrogen substituent becomes more bulky. These results are in accordance with our previous investigation of the structures of N-monosubstituted 2-phenylacetamides. © 1986.