Palladium-catalyzed aryl halide carbonylation-intramolecular O-enolate acylation: efficient isocoumarin synthesis, including the synthesis of thunberginol A

Exposure of a series of alpha-(o-haloaryl)-substituted ketones to palladium-catalyzed carbonylation conditions leads to the formation of the corresponding isocoumarins. Balloon pressure of CO is sufficient to achieve high yielding reactions, and both cyclic and acyclic ketones are efficient substrates. The utility of the method is illustrated by a short synthesis of the natural product thunberginol A.