Silica supported tungstic acid (STA): an efficient catalyst for the synthesis of bis-spiro piperidine derivatives under milder condition

A mild, efficient, and expeditious method has been developed for the synthesis of 3,5-dispirosubstituted piperidines via a three component, one-pot cyclocondensation reaction of aromatic amines, formaldehyde, and dimedone using Silica supported tungstic acid as heterogeneous catalyst for the first time. The reaction involving formation of six new covalent bonds was conveniently promoted by Silica supported tungstic acid and the catalyst could be recovered easily after the reaction and reused without any loss of its catalytic activity. The advantageous features of this methodology are high atom-economy, operational simplicity, shorter reaction time, convergence, and facile automation.