Ring-Closing Reaction of Allenic/Propargylic Anions Generated by Base Treatment of Sulfonylallenes

The intramolecular trapping of allenyl/propargyl anions generated by base treatment of sulfonylallenes was investigated. Treatment of 1-(ω-iodoalkyl)-1-(phenylsulfonyl)allenes with TBAF or NaH in DMF efficiently produced three- to seven-membered 1-ethynyl-1-(phenylsulfonyl) substituted carbocycles. The allenyl/propargyl anions could also be intramolecularly trapped using a terminal aldehyde or α,β-unsaturated ester. The phenylsulfonyl group was found to be replaced by other electron-withdrawing functionalities like ketone and ester groups but not by an alkyl group for this novel ring-closing reaction.