Studies of chromenes. Part 8. Addition versus rearrangement in silver ion-assisted solvolyses of trihalogenocyclopropa[c]chromenes

Abstract

Silver ion-assisted solvolysis of the trichlorocyclopropa[c]chromene (1) at 80 °C proceeds by addition to give the 3-dichloromethylenechroman-4-one (2). At higher temperatures solvolysis involves cyclopropyl-allyl rearrangement and yields derivatives of the 4-dichloromethylenechroman-3-ol. The 7b-bromo-1,1-dichlorocyclopropa[c]chromene (9) reacts by rearrangement even at 80 °C.