ONE-POT SYNTHESIS OF CYCLOBUTANOLS BY RING EXPANSION OF OXASPIROPENTANES INDUCED BY GRIGNARD-REAGENTS

Aromatic, aliphatic and vinylic Grignard reagents efficiently catalyze the ring expansion of oxaspiropentanes 2a,b to give, in one pot, good yields of cyclobutanols 3a, 3b-7b. Benzyl magnesium chloride gives a mixture of cyclobutanols and the cyclopropanol 8, probably coming from a direct nucleophilic attack on the epoxide part of the oxaspiropenta ne.