NMR SPECTROSCOPIC AND COMPUTATIONAL CHARACTERIZATION OF 1-(P-ANISYL)VINYL CATIONS - METHOXY GROUP ROTATION AS A PROBE OF C-BETA-SI, C-BETA-C, AND C-BETA-H HYPERCONJUGATION

被引：71

作者：

SIEHL, HU ^{[1
]}

KAUFMANN, FP ^{[1
]}

HORI, K ^{[1
]}

机构：

[1] YAMAGUCHI UNIV,FAC LIBERAL ARTS,DEPT CHEM,YAMAGUCHI 753,JAPAN

来源：

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY | 1992年 / 114卷 / 24期

关键词：

D O I：

10.1021/ja00050a014

中图分类号：

O6 [化学];

学科分类号：

0703 ;

摘要：

The 1-(p-anisyl)-2-(triisopropylsilyl)vinyl cation 1 and the 1-(p-anisyl)vinyl cation 2 were generated in solution and characterized by NMR spectroscopy. Ab initio molecular orbital calculations using the 6-31G basis set were performed for cation 2, the 1-(p-anisyl)-2-methylvinyl cation 3, and the 1-(p-anisyl)-2-silylvinyl cation 4, serving as a model cation for 1, to elucidate the importance of alpha-pi aryl stabilization and beta-sigma bond stabilization in 1-(p-anisyl)vinyl cations with various beta substituents. For comparison, the p-anisylmethyl cation 5 was also calculated. The para carbon chemical shifts, the experimentally determined and calculated torsional barriers around the phenyl-methoxy C-O bond, and the computed geometrical parameters and charges are used to determine the contributions of conjugative and hyperconjugative stabilization effects in 1-(p-anisyl)vinyl cations. The ability of beta substituents to hyperconjugatively donate electrons to the empty cationic orbital follows the order silyl > methyl > H.

引用

页码：9343 / 9349

页数：7

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