Neighbouring-group influence on the ring opening of 2-aryloxymethyl-1,1,2-tribromocyclopropanes under phase-transfer conditions

When a number of 2-aryloxymethyl-1,1,2-tribromocyclopropa were treated with sodium hydroxide and ethanol under phase-transfer conditions, ring opening occurred to give mixtures of acetylenic diethyl acetals and ketals in bett er than 80% total isolated yield. The acetylenic diethyl ketals predominate d significantly and were, in some cases, almost the exclusive product. It i s argued that this ketal selectivity is in part caused by hydrogen bonding between ethanol and the aryloxy group.