Dehydrohalogenation of some tetrahalogenobicyclo[4.1.0]hept-3-enes. Formation and decomposition of 1,1-dihalogenocyclopropabenzenes

Abstract

Of the tetrahalogenobicyclo[4.1.0]hept-3-enes (2)–(7) only the tetrachloro-2,5-diphenyl derivative (3) yields an isolable gem-dihalogenocyclopropabenzene (10) on dehydrochlorination. The formation of esters and orthoesters from compounds (2) and (4)–(6) is explicable in terms of the cyclopropabenzenes (9) and (11)–(13) as intermediates. The decomposition of (10) in protic media has been studied and is believed to proceed via a cyclopropabenzenylium ion (30).