Pd/C: An efficient and reusable catalyst for the synthesis of flavones via carbonylation of aryl halides

This work describes an efficient and mild approach for the synthesis of flavones via catalytic carbonylation of aryl halides with 2-hydroxyacetophenone using the commercial Pd/C as an efficient, heterogeneous and recyclable catalyst. Under balloon pressure of CO, 0.6mol% Pd/C is sufficient for moderate yields of flavones for the carbonylation of aryl iodides under phosphine-free conditions and aryl bromides in the presence of phosphine ligand. The catalyst is easily separable and shows significant recyclability. Moreover, the reaction mechanism was discussed, and a possible mechanism that contains two different cyclisation pathways was proposed.