Evidence for a stepwise addition of carbenes to strained double bonds: Reactions of dihalocarbenes with cyclopropenes

Article abstract of DOI:10.1002/anie.199716231

Zwitterionic species are most likely the intermediates for the formation of 1,1-dihalo-2,3-diarylbutadienes by addition of dihalocarbenes to 1,2-diarylcyclopropenes [Eq. (a)]. Bicyclobutanes can be ruled out as intermediates for the formation of butadiene