Synthesis of 3‐Keto Pyridines from the Conjugated Allenone – Alkynylamine Oxidative Cyclization Catalyzed by Supported Au Nanoparticles

Abstract

Abstract Recyclable supported Au nanoparticles on TiO 2 catalyze the cyclization of N ‐propargyl or N ‐homopropargyl β‐enaminones followed by dehydrogenation (aromatization) leading to substituted 3‐keto pyridines or 4‐picolines in very good yields. This pathway is in contrast to their known cyclization in the presence of Au(I) or Au(III) catalysts which provides 1,4‐oxazepines, instead. The enaminones are formed in situ upon mixing a conjugated allenone or allenyl ester with the alkynylamine, thus the pyridine‐forming transformation is typically a one pot process. magnified image