Four-component stereoselective synthesis of tetracyano-substituted piperidines

Abstract

A novel four-component stereoselective synthesis of polysubstituted piperidines is reported. The Knoevenagel–Michael–Mannich cascade of two equivalents of aromatic aldehydes, formaldehyde, two equivalents of malononitrile and ammonium acetate provides convenient access to the 2,6-diaryl-3,3,5,5-tetracyanopiperidines in good to excellent yields. Ammonium acetate plays a role both as a catalyst and as a nitrogen source. The formation of products is highly stereoselective. Structures of the synthesized compounds were confirmed by 1H NMR, 13C NMR, IR, elemental analysis and mass spectral studies. 2,6-diphenylpiperidine-3,3,5,5-tetracarbonitrile was characterized by X-ray diffraction.