Synthesis of highly functionalized piperidines via one-pot five-component reactions in the presence of Cr(NO O

A simple and efficient method is described for one-pot five-component synthesis of highly functionalizaed piperidines from ?-keto esters, aromatic aldehydes and various amines in the presence of a catalytic amount of Cr(NO3)3.9H2O in ethanol at room temperature. The main features of current protocol include mild reaction conditions, easy work up, and good yields.