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.