Preparation and reactivity of arylsulfonyl substituted cyclopropenes

Abstract A study of the cycloaddition behavior of several arylsulfonyl substituted alkynes with 2-diazopropane has been carried out. These activated acetylenes react to give 3H-pyrazoles which extrude nitrogen on photolysis to produce cyclopropenes in high yield. Soft nucleophiles such as thiophenoxide readily add to the activated pi-bond to give thiophenyl substituted cyclopropanes. Reaction of 1-phenylsulfonyl-2,3,3-trimethylcyclopropene with n-butyllithium followed by alkylation with various electrophiles produces arylsulfonyl substituted methylene cyclopropanes. These compounds undergo thermal rearrangement to the thermodynamically more stable isopropylidine cyclopropane.