Intramolecular [4+2]-cycloadditions of nitroalkenes with olefins. 2
作者:Scott E. Denmark、Young-Choon Moon、Christopher J. Cramer、Michael S. Dappen、C.B.W. Senanayake
DOI:10.1016/s0040-4020(01)89054-2
日期:1990.1
The intramolecular [4+2]-cycloadditions of di- and trisubstituted nitroalkenes with unactivated olefins are described. The cycloadditions proceed readily at low temperatures in the presence of SnCl4. The reactions are shown to be stereospecific in the preservation of dienophile configuration in the product. The configuration of the heterodiene controls the stereochemistry of the ring fusion but the
描述了二和三取代的硝基烯烃与未活化的烯烃的分子内[4 + 2]-环加成。在存在SnCl 4的情况下,环加成反应在低温下容易进行。在保持产物中的亲双烯体构型方面,反应显示为立体特异性的。杂二烯的构型控制环稠合的立体化学,但是只有三取代的硝基烯烃才具有很高的选择性。一环加成率顺亲二烯物是CA。比反双亲嗜酒者快20倍。讨论了机制和过渡结构的含义