NHC-Ag(I)-Catalyzed Three-Component 1,3-Dipolar Cycloaddition To Provide Polysubstituted Dihydro-/Tetrahydrofurans

A new method was developed to synthesize polyfunctionalized dihydrofuran and tetrahydrofuran derivatives from the three-component [2 + 2 + 1] cycloaddition of the diazoesters with aryl/alkenyl aldehydes and alkyne/olefin dipolarophiles by using a Ag­(I) <i>N</i>-heterocyclic carbene complex as the catalyst. A carbonyl ylide intermediate was generated, which undertook an <i>endo</i>-type 1,3-dipolar cycloaddition to provide the desired dihydro-/tetrahydrofurans in high regio- and diastereoselectivities by using α-aryl or α-alkenyl diazoesters