Rhodium-Catalyzed C4-Selective C–H Alkenylation of 2-Pyridones by Traceless Directing Group Strategy

A rhodium-catalyzed C4-selective C–H alkenylation of 3-carboxy-2-pyridones with styrenes has been developed. The carboxylic group at the C3 position works as the traceless directing group, and the corresponding C4-alkenylated 2-pyridones are obtained exclusively with concomitant decarboxylation. Unlike the reported procedures, the exclusive C4 selectivity is uniformly observed even in the presence of potentially more reactive C–H bonds at the C5 and C6 positions. By using this strategy, the multiply substituted 2-pyridone can be prepared via sequential C–H functionalization reactions.