Unlocking σ-Type Cyclopropenium Cation Transfer Reactions by an Iodine(III)-Based Umpolung Strategy

σ-Type cyclopropenium cations (CPCs), which are formally generated by removing one substituent on the alkene of cyclopropenes, represent promising intermediates for forging functionalized cyclopropenes. However, σ-type CPCs are challenging to access and their synthetic utility remain largelyunexplored. Recently, we introduced electrophilic cyclopropenyl-gold(III) species as equivalents of σ-type CPCs, which can then react with terminal alkynes or vinylboronic acids to afford alkynyl- or alkenyl-cyclopropenes.The merging of redox gold catalysis and a new class of hypervalent iodine reagents—the cyclopropenyl benziodoxoles (CpBXs)—plays a central role in generating the σ-type CPC equivalents. With the same reagents, we have also developed a synergistic Au/Ag bimetallic catalytic cyclopropenyl cross-coupling system that enables to forge 1,1'-bicyclopropenyl derivatives in an efficient and modular manner. Our strategy provides access to previously inaccessible, yet highly useful, functionalized cyclopropenes, thereby significantly advancing both cyclopropene and hypervalent iodine chemistry.

Publication History

Received: 20 January 2025

Accepted: 07 February 2025

Accepted Manuscript online:
07 February 2025