Aza-Michael Mono- and Bis-Addition of primary and secondary amines promoted by silica-supported polyphosphoric acid, PPA/SiO2

Abstract

The development of new protocols using non-toxic, low cost, eco-friendly, recyclable catalyst systems which give high productivity under mild reaction conditions has received much attention in organic synthesis in the last couple of years. A collection of structurally diverse β-amino carbonyl compounds was successfully synthesized by aza-Michael mono- and double-additions using silica-supported polyphosphoric acid as catalyst under solventless conditions. Highlighted advantages of this particular catalyst include ease of preparation and long-term stability under storage.