Nendel M, Sperling D, Wiest O, Houk KN
Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569 and Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556-5670, USA.
J Org Chem. 2000 Jun 2;65(11):3259-68. doi: 10.1021/jo991026f.
The rearrangements and stereoisomerizations of four systems, vinylcyclopropane, 4-tert-butylvinylcyclopropane, 5-methylvinylcyclopropane, and 2,5-dimethylvinylcyclopropane, as well as a variety of deuterated derivatives and 1- and 2-methyl-, methoxy-, difluoro-, and amino-substituted species, were studied by density functional theory calculations using the B3LYP functional and the 6-31G basis set. Energies were evaluated with CASSCF(4, 4)/6-31G single point calculations. The major product is obtained by the si pathway. Structures on this path are essentially pure diradical in character. Higher energy diradical species and intermediates are responsible for the scrambling of the stereochemistry. The stereoselectivity of the reaction is increased by substituents which increase the relative energy of the species involved in competing stereoselectivities. The computed secondary kinetic isotope effects reproduce the experimental values reported in the literature.
采用密度泛函理论计算方法，使用B3LYP泛函和6 - 31G基组，对四种体系（乙烯基环丙烷、4 - 叔丁基乙烯基环丙烷、5 - 甲基乙烯基环丙烷和2,5 - 二甲基乙烯基环丙烷）以及多种氘代衍生物和1 - 甲基、2 - 甲基、甲氧基、二氟和氨基取代的物种的重排和立体异构化进行了研究。能量通过CASSCF(4, 4)/6 - 31G单点计算进行评估。主要产物通过si途径获得。该途径上的结构本质上具有纯双自由基的特征。较高能量的双自由基物种和中间体导致立体化学的混乱。反应的立体选择性通过增加参与竞争立体选择性的物种的相对能量的取代基而提高。计算得到的二级动力学同位素效应与文献报道的实验值相符。
