Ylide-Induced Ring Contraction of Coumarins to Benzofurans: Applications to the Synthesis of Bis-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 bis-heterocycles under both metal and metal-free conditions. The synthetic utility of this method is illustrated through the synthesis of known bioactive compounds. Detailed mechanistic investigations and quantum chemical calculations have provided valuable insights into the mechanism of the ring contraction reaction.