Photosensitizer-free visible-light-induced gold-catalyzed tandem cyclization/arylation of 2,3-allenamides with aryl diazonium salts: an efficient synthesis of 4-aryl-2(5H)-furanimine and furanone derivatives

Abstract

A novel gold-catalyzed tandem intramolecular arylative cyclization of 2,3-allenamides with readily accessible aryl diazonium salts under visible-light irradiation has been developed. This method enables the efficient synthesis of 4-aryl-2(5H)-furanimine and furanone derivatives under mild conditions, without the need for external photosensitizers and oxidants. Notably, this approach accomplishes, for the first time, the synthesis of 4-aryl-2(5H)-furanimines from 4-monosubstituted 2,3-allenamides via an O-attack pathway, overcoming the limitations of conventional methods and bridging a critical gap in accessing 4-aryl-2(5H)-furanimine derivatives from such substrates. Furthermore, product selectivity is exclusively controlled by solvent: using 1,4-dioxane yields furanimines, while moist methanol gives furanones, both in moderate to excellent yields. The reaction demonstrates broad functional group tolerance and a wide substrate scope, providing a highly versatile one-pot strategy for constructing two distinct heterocyclic frameworks from 2,3-allenamides. Mechanistic studies provide strong support for the proposed reaction pathway.