Using only 10% of CrCl2 as catalyst, manganese-powder as reducing agent and TMSCl as scavenger, 2-methylene-α,Ï-dialdehydes and -ketones can be coupled to form cyclic diols diastereoselectively. The diastereomeric excess strongly depends on the ring size and the substituents of the Ï-carbonyl group. The greater the ring size the higher diastereoselectivities are observed. In all cases cis-diols are preferentially formed.
仅使用CrCl2的10%作为催化剂、
锰粉作为还原剂和TMSCl作为清除剂,2-亚甲基-α,ω-二醛和二酮可以立体选择性地耦合形成环状二醇。立体异构过量强烈依赖于环的大小和ω-羰基的取代基。环越大,观察到的立体选择性越高。在所有情况下,优先形成顺式二醇。