Facial Selectivity and Stereospecificity in the (4 + 3) Cycloaddition of Epoxy Enol Silanes
摘要:
The scope of the (4 + 3) cycloaddition using epoxy enol silanes has been examined. Unhindered and nucleophilic dienes react to give the highest yields, but hindered dienes give rise to higher diastereoselectivities. Notably, the cycloaddition shows facial selectivity and stereospecificity for the stereochemistry of the epoxy enol silane.
Asymmetric (4+3) Cycloadditions of Enantiomerically Enriched Epoxy Enolsilanes
作者:Brian Lo、Sarah Lam、Wing-Tak Wong、Pauline Chiu
DOI:10.1002/anie.201207427
日期:2012.11.26
A f(oxy) allyl: The intermolecular (4+3) cycloaddition of enantiomericallyenriched epoxy enolsilanes produces cycloadducts with up to 99 % ee, thus implying the reaction does not proceed by the putative achiral oxyallyl cation intermediate, but through a transiently chiral electrophile which retains the stereochemical information of the epoxide (see scheme; TES=triethylsilyl, Tf=trifluoromethanesulfonyl)