硅烯醇醚的光诱导电子转移(PET)已被用来合成多种稠环系统。然而,由于底物范围窄、产物收率低、立体选择性和区域选择性不理想,该方法的适用性受到限制。在此,我们报道了 PET 触发的甲硅烷基烯醇化物级联反应,导致形成有角度稠合的三环支架。该反应表现出广泛的底物范围和优异的立体选择性。通过 DFT 计算和构象分析阐明了该级联反应的区域选择性和立体选择性。
A Bifunctional Lewis Acid Induced Cascade Cyclization to the Tricyclic Core of <i>ent</i>-Kaurenoids and Its Application to the Formal Synthesis of (±)-Platensimycin
作者:Lizhi Zhu、Yejian Han、Guangyan Du、Chi-Sing Lee
DOI:10.1021/ol3033412
日期:2013.2.1
A mild and efficient bifunctional Lewis acid induced cascade cyclization reaction has been developed for construction of the tricyclic core of ent-kaurenolds. With ZnBr2 as the bifunctional Lewis acid, a series of substituted enones and dienes underwent cascade cyclization smoothly at room temperature and provided the tricyclic products in one pot with good yields (75-91%) and high diastereoselectivity. The cyclized product has been successfully employed for the formal synthesis of (+/-)-platenslmycln.