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 oxaspiropentane.