The CF3SO3H-promoted ring opening of gem-difluorocyclopropyl ketones prefers to undergo proximal bond cleavage and the subsequent cyclization with nitriles occurred smoothly to give 2-fluoropyrroles.
Boron trihalide-promoted ring-opening reactions of gem-difluorocyclopropyl ketones to give the corresponding β-trifluoromethyl ketones and β-halodifluoromethyl ketones were described. It was found that boron trihalides act as both Lewis acids and nucleophiles and the proximal bond prefers to cleave in this transformation.