Selective preparation of (Z)- and (E)-prop-1-enylamides from N-allylbenzamides

A series of para-substituted N-allylbenzamides was submitted to isomerization under basic conditions. With LDA at −78°C, the corresponding (E)-N-(prop-1-enyl)benzamide was the major product. With n-butyllithium and the mixture warmed to 0°C, the (Z)-isomer was essentially furnished.