Concise synthesis of stereodefined dienols and cyclopentadienes via direct addition of 1-bromomagnesiobutadienes and 1-lithiobutadienes to carbonyl compounds

Stereodefined all-cis substituted dienols could be readily prepared in excellent yields by the direct addition of 1-bromomagnesiobutadiene or 1-lithiobutadiene derivatives with aldehydes and ketones. Depending on the nature of substituents and workup procedures, multi-substituted cyclopentadienes could be also formed in high yields from these dienols. It is interesting to note that, unlike normal alkenyl magnesiumbromides, these conjugated butadienyl magnesiumbromide reagents do not react with ketones.