Photocatalytic synthesis of carbamoylated chroman-4-ones via radical cascade cyclization of 2-(allyloxy)arylaldehydes and oxamic acids

Abstract

Chroman-4-one is a key structural motif widely distributed in natural products and pharmaceuticals. Similarly, the amide functionality serves as another pharmacologically important moiety, widely present in bioactive natural products and drug molecules. Consequently, we developed a photosensitiser-free photocatalytic method for synthesising amide-substituted chroman-4-ones though a decarboxylative radical cascade cyclisation reaction. This transformation was initiated by the visible light/benzoyl peroxide (BPO)-mediated generation of carbamoyl radicals from oxamic acids, which subsequently underwent addition/cyclisation with 2-(allyloxy)arylaldehydes. The method requires mild conditions and shows operational simplicity and a broad substrate scope, enabling the efficient generation of diverse chroman-4-one derivatives without the need for transition-metal catalysts or additional photosensitisers.