Department of Chemistry, University of Connecticut , 55 North Eagleville Road, Storrs, Connecticut 06269-3060, United States.
Department of Chemistry, Yale University , 275 Prospect Street, New Haven, Connecticut 06520-8107, United States.
Org Lett. 2017 Dec 1;19(23):6408-6411. doi: 10.1021/acs.orglett.7b03287. Epub 2017 Nov 16.
Base-catalyzed equilibration of anancomeric cyanocyclohexanes demonstrates that replacement of cis-3,5-dimethyl holding groups with electron-withdrawing CF groups dramatically increases the proportion of the axial cyano isomer present at equilibrium. The CF groups exert an effect on the conformational energy of the cyano group worth about 0.6 kcal/mol. A nonclassical hydrogen bond between the axial CN group and the syn-axial hydrogens is a major contributor to the axial stability of the group.
基于碱的对映选择性氰基环己烷平衡反应证明，用吸电子的 CF 取代顺式-3,5-二甲基取代基，可极大增加氰基异构体在平衡状态下的比例。CF 取代基对氰基的构象能产生约 0.6 kcal/mol 的影响。轴向 CN 基团和同轴向氢原子之间的非经典氢键是该基团轴向稳定性的主要贡献者。
