One-pot five-component synthesis of highly functionalized piperidines using oxalic acid dihydrate as a homogenous catalyst

An efficient green protocol is described for the preparation of highly functionalized piperidines via a one-pot five-component reaction between aromatic aldehydes, anilines and β-ketoesters in the presence of oxalic acid dihydrate as catalyst in ethanol at ambient temperature. The structure as well as the relative stereochemistry of these compounds was confirmed by single X-ray crystallographic analysis.