An efficient synthesis of 5-silyl-2,3-dihydrofurans via acid-catalyzed ring-enlargement of cyclopropyl silyl ketones and their functionalization

Treatment of cyclopropyl silyl ketones with trimethylsilyl trifluoromethanesulfonate as a strong acid having low nucleophilic counter anion gives the corresponding 5-silyl-2,3-dihydrofuran derivatives, exclusively, regardless of substituents on the cyclopropane ring or silicon atom. The resulting 5-silyl-2,3-dihydrofuran derivatives exhibit both reactivities of the vinylsilane and the cyclic enol ether in the subsequent reaction with electrophilic reagents or Heck type reaction.