Ylide-Induced Ring Contraction of Coumarins to Benzofurans: Applications to the Synthesis of -Heterocycles.

We report an unusual ring contraction of 4-chlorocoumarin to benzofuranoyl sulfoxonium ylides using a Corey-ylide. These stabilized ylides were subsequently utilized for the synthesis of various valuable -heterocycles under both metal and metal-free conditions. The synthetic utility of this method is illustrated through the synthesis of known bioactive compounds.