期刊
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
卷 60, 期 27, 页码 14989-14997出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.202101809
关键词
cyclic allenes; cycloadditions; density functional theory; diastereoselectivity; substituent effects
资金
- NIH NIGMS [R01 GM123299, R01 GM132432, R35 GM139593, F31 GM130099-02]
- National Science Foundation [CHE-1764328]
- Austrian Science Fund (FWF) [J 4216-N28]
- City of Vienna [H-331849/2018]
- Natural Science Foundation of Jiangsu Province, China [BK20190505]
The Diels-Alder reactions of furans and pyrroles with 1,2-cyclohexadiene and oxa- and azaheterocyclic analogs exhibit endo selectivity, which is determined by the interaction of molecular orbitals and electrostatic effects. This selectivity, based on stabilizing interactions, is expected to lead to the increased use of strained cyclic allenes in chemical synthesis.
Strained cyclic allenes, first discovered in 1966 by Wittig and co-workers, have recently emerged as valuable synthetic building blocks. Previous experimental investigations, and computations reported here, demonstrate that the Diels-Alder reactions of furans and pyrroles with 1,2-cyclohexadiene and oxa- and azaheterocyclic analogs proceed with endo selectivity. This endo selectivity gives the adduct with the allylic saturated carbon of the cyclic allene endo to the diene carbons. The selectivity is very general and useful in synthetic applications. Our computational study establishes the origins of this endo selectivity. We analyze the helical frontier molecular orbitals of strained cyclic allenes and show how secondary orbital and electrostatic effects influence stereoselectivity. The LUMO of carbon-3 of the allene (C-3 is not involved in primary orbital interactions) interacts in a stabilizing fashion with the HOMO of the diene in such a way that the carbon of the cyclic allene attached to C-1 favors the endo position in the transition state. The furan LUMO, allene HOMO interaction reinforces this preference. These mechanistic studies are expected to prompt the further use of long-avoided strained cyclic allenes in chemical synthesis.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据