Studies in the cycloproparene series: cycloaddition reactions of diarylmethylidenecycloproparenes

Journal ArticleDiarylmethylidenecyclopropanaphthalenes 4b-d add diphenylisobenzofuran (DPIBF) and α-pyrone across the exocyclic double bond to give ring expanded products 11b-d and 13b-d that result from subsequent relief of ring strain in the non-isolable spirocyclic intermediates 10 and 12, respectively. The benzene homologues 3b and 3c add DPIBF across the bridge bond to give the norcaradiene adducts 19b and 19c