1,2-Bisanionic Coupling Approach to 2,3-Disubstituted Cyclopentenols and Cyclopentenones

We describe a new approach to 2,3-disubstituted cyclopentenols and cyclopentenones through two consecutive regioselective additions of equal or different electrophiles to a cyclopentene bisanionic synthon. Indeed, on exposure to BuLi, 3-bromo-2-iodocyclopent-2-enol O-TBS ether undergoes iodine−lithium permutation with complete regioselectivity. Successive reaction of the monolithium anion with different C(sp²)- and C(sp³)-electrophiles affords the corresponding 2-substituted-3-bromocyclopentenol derivative. Subsequent bromo−lithium exchange with t-BuLi, followed by reaction with an equal or different electrophile, affords the desired 2,3-disubstituted cyclopentenol.