Diastereoselective, Catalytic Access to Cross‐Aldol Products Directly from Esters and Lactones

High oxidation-state carbonyl coupling partners including esters and lactones were reacted with enones to give aldol-type products directly using two-fold organoborane catalysis. This new retrosynthetic disconnection is compatible enolisable partners, without self-condensation, couples the high reactivity of secondary dialkylboranes stability pinacolboronic esters. Excellent chemoselectivity, substrate scope (including those containing reducible functionalities free alcohols) diastereocontrol achieved access both syn- anti-aldol-type products. Mechanistic studies confirmed catalytic role single borane catalyst for boron enolate formation an aldehyde surrogate from ester or lactone partner.