Stereoselective reactions. I. A highly efficient asymmetric synthesis of .BETA.-substituted aldehydes via 1,4-addition of Grignard reagents to optically active .ALPHA.,.BETA.-unsaturated aldimines.
作者:SHUNICHI HASHIMOTO、SHUNICHI YAMADA、KENJI KOGA
DOI:10.1248/cpb.27.771
日期:——
The 1, 4-addition of Grignard reagents to the chiral α, β-unsaturated aldimines (3d, e), prepared from α, β-unsaturated aldehydes (1) and optically active tert-leucine tert-butyl ester (2d), afforded, after hydrolysis, optically active β-substituted aldehydes (4) in 91-98% enantiomeric excess. The present method has advantages in giving aldehydes (4) in high enantiomeric purities, allowing easy preparation of the aldimines as well as easy recovery of optically active tert-leucine tert-butyl ester (2d) without any racemization for reuse, and exhibiting general utility. The possible mechanism of the reaction, by which the absolute configuration of the aldehydes (4) is unequivocally predictable, is proposed.
格里尼亚尔试剂对手性α, β-不饱和醛亚胺(3d, e)的1, 4-加成反应,是通过α, β-不饱和醛(1)和光学活性的tert-亮氨酸tert-丁基酯(2d)制备的,经过水解后获得了光学活性的β-取代醛(4),其对映体过量为91-98%。该方法在提供高对映体纯度的醛(4)方面具有优势,能够简便地制备醛亚胺,并且能够轻松回收光学活性的tert-亮氨酸tert-丁基酯(2d),而不会发生消光,从而可重复使用,且具有广泛的适用性。提出了该反应的可能机制,通过该机制,可以明确预测醛(4)的绝对构型。