Studies in the Cycloproparene Series: Cycloaddition Reactions With 1,3-Diphenylisobenzofuran

Abstract

The behaviour of cyclopropabenzene (1) with 1,3-diphenylisobenzofuran ( dpibf ) is temperature dependent. Addition to the strained bridge bond of (1) gives the Diels -Alder adduct (13) in tetrahydrofuran at 20°C, but in chloroform at the same temperature the ring-expanded 5,10-epoxydibenzocycloheptene (12) is also formed. Compound (12) becomes the sole product from reaction at 30°C or higher. Cyclopropa [b]naphthalene (2) is inert to dpibf under similar conditions but provides the dimer 6,13-dihydropentacene (15). The triazoloindazole (19) results from reaction of (2) with 4-phenyl-3H-1,2,4-triazole-3,5(4H)- dione.