Direct Amide Formation via Carbamoylation of Aromatic Bromides using Heteropoly Acid and UV-Light

We performed direct carbamoylation using heteropoly acid (HPA) photocatalysts with a Keggin structure under UV-light. Carbamoyl radicals were generated via the decarboxylation of N,N-disubstituted dimethyloxamic acid under these conditions. The HPA catalyst functioned as a photocatalyst when the dicarbonyl bond was broken, generating carbon dioxide. We found that disubstituted carbamoyl radicals readily coupled with aromatic bromides to generate diverse benzoic amides. In particular, using a homogeneous HPA photocatalyst improved the reaction's transmittance, which had been a problem of the existing heterogeneous photocatalyst. This reaction condition can be easily handled, mild, and safer than the traditional benzoic amide synthesis. This method can be scaled up efficiently, is eco-friendly, and can be applied to producing active pharmaceutical ingredients.