Using only 10 mol% of CrCl2 as catalyst, acroleins and α,β-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 R1 of the unsaturated carbonyl compound. Formation of the syn-diols is preferred with sterically demanding R1, the anti-diols are obtained with smaller substituents.
以
锰粉末为还原剂,TMS-Cl 为清除剂,仅用 10 mol% 的
氯化
铬作为催化剂,就可将
丙烯醛和 δ、δ-不饱和酮与脂肪醛偶联,得到取代的 1,2
-二醇。非对映选择性取决于取代基,尤其是不饱和羰基化合物的 R1。形成合成二元醇的 R1 具有较高的立体要求,而形成反二元醇的取代基则较小。