Second Generation CaSH (Camphor Sulfonyl Hydrazine) Organocatalysis. Asymmetric Diels-Alder Reactions and Isolation of the Catalytic Intermediate
作者:Qinghua Li、Wai-Yeung Wong、Wing-Hong Chan、Albert W. M. Lee
DOI:10.1002/adsc.201000438
日期:2010.9.10
chiral auxiliary, Oppolzer’s camphor sultam, is turned into the new generation camphor sulfonyl hydrazine (CaSH II) organocatalyst. With the primary hydrazine functionality external to the tricyclic structure, CaSH II is active towards ketone substrates in asymmetric Diels–Alder reactions. The iminium intermediate of the catalytic cycle was isolated. When it was put back into the solution reaction system
第一步,将众所周知的手性助剂Oppolzer的樟脑sultam转变为新一代樟脑磺酰肼(CaSH II)有机催化剂。在三环结构外部具有伯肼功能,CaSH II在不对称Diels-Alder反应中对酮底物具有活性。分离出催化循环的亚胺中间体。当将其放回溶液反应系统中时,观察到相同水平的产率和立体选择性。基于这些观察,我们认为有机催化剂实际上是一种原位手性助剂。