Uncatalyzed, Solvent-Free [2+2] Cycloaddition of Cyclic Ketene Trimethylsilyl Acetals with Electrophilic Acetylenes

Abstract

Abstract Cyclic ketene trimethylsilyl acetals reacted with electrophilic acetylenes (ethyl propynoate, dimethyl acetylenedicarboxylate and ethynyl methyl ketone) to afford the corresponding [2+2] cycloadducts. The reactions were run at room temperature, without a catalyst and under solvent-free conditions. α-Alkylidenelactones, ?-oxocyclobutanecarboxylates and substituted furan derivatives proved to be readily available from the [2+2] cycloadducts by treatment either with TBAF in THF solution or with BF3·Et2O.