Stereoinduced cyclization of acyloxyalkenes using iodosylbenzene via a 1,3-dioxan-2-yl cation

Reactions of pent-4-en-2-yl carboxylates and their derivatives with iodosylbenzene gave 2,4-disubstituted and 2,3,5-trisubstituted tetrahydrofurans with high diastereomeric ratio. The tetrahydrofuranylation may proceed via a 1,3-dioxan-2-yl cation intermediate generated by the participation of the internal acyloxy group in electrophilic attack of hypervalent iodine(III) toward acyloxyalkenes. Steric regulation owing to the cyclic structure of the cation accounts for the high stereoselectivity of the tetrahydrofuranylation.