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.