Graphitic carbon nitride/nickel dual catalysis for decarboxylative synthesis of unsymmetrical ketones from keto acids

Abstract

We report a sustainable, dual-catalytic system for the synthesis of ketones via decarboxylative cross-coupling of α-keto acids and aryl halides, enabled by graphitic carbon nitride (gCN) and nickel catalysis. The heterogeneous gCN photocatalyst, derived from earth-abundant precursors, facilitates the generation of acyl radicals under light irradiation, which undergo efficient nickel-catalysed cross-coupling to form a diverse array of ketone products. The methodology demonstrates broad substrate scope, including heteroaryl and vinyl halides, and is compatible with a range of functional groups. Our studies revealed and addressed a competing Norrish Type II cleavage pathway, enabling the successful coupling of longer-chain substrates by switching to a 456 nm light source. Oxamic acids were shown to participate under similar conditions to furnish amides. Compared to iridium-based systems, this protocol significantly reduces total carbon release (TCR), and the gCN photocatalyst was readily recycled over 10 runs without loss of activity. This work highlights gCN's potential as a green, reusable alternative for metallaphotoredox cross-couplings.