Stereoselective conjugate addition of aryl- and alkenylboronic acids to acyclic γ,δ-oxygen-substituted α,β-Enoates

The substrate-controlled Rh-I-catalyzed conjugate addition of aryl- and alkenylboronic acids to alpha,beta-unsaturated esters which bear gamma- and delta-oxygen substituents takes place in a highly anti diastereoselective fashion either when using gamma-hydroxyl unprotected starting materials or when the gamma-oxygen substituent is protected with a nonbulky group. The delta-oxygen substituent plays a role in the stereoselectivity of the reaction, and better results are obtained when this OH-group is protected.