A facile diastereoselective synthesis of functionalized 1,2,3-trisubstituted benzocyclopentenes through the cycloaddition of bis(phenylsulfonyl)iodonium ylides to cyclic alkenes.

The thermal cycloaddition of beta-disulfonyl iodonium ylides to cyclic alkenes affords exclusively 1,2,3-trisubstituted cis(1,2)/cis(2,3)-configured benzocyclopentenes by an electrophilic attack of the ylide on the olefinic double bond. This unsual transformation provides a convenient and direct method for the diastereoselective synthesis of functionalized bicyclo[3.3.0]octanes (characteristic structural units contained in polyquinane natural products), when cyclopentenes are used as cycloalkene partner.