Chromium(II)-Catalyzed Diastereoselective Pinacol Type Cross Coupling between α,β-Unsaturated Carbonyl Compounds and Aliphatic Aldehydes

Using only 10 mol% of CrCl2 as catalyst, acroleins and , -unsaturated ketones were coupled with aliphatic aldehydes to obtain substituted 1,2-diols using manganese powder as reducing agent and TMS-Cl as scavenger. Diastereoselectivities depend on the substituents especially on R 1 of the unsaturated carbonyl com- pound. Formation of the syn-diols is preferred with sterically de- manding R 1 , the anti-diols are obtained with smaller substituents.