DYNAMIC STEREOCHEMISTRY OF TRI(2-METHYL-1-AZULENYL)METHYL CATION - STERIC EFFECT OF 2-METHYL GROUPS ON ROTATIONAL BARRIERS AND MECHANISM

被引：18

作者：

ITO, S ^{[1
]}

MORITA, N ^{[1
]}

ASAO, T ^{[1
]}

机构：

[1] TOHOKU UNIV,FAC SCI,DEPT CHEM,AOBA KU,SENDAI,MIYAGI 980,JAPAN

来源：

TETRAHEDRON LETTERS | 1994年 / 35卷 / 22期

关键词：

D O I：

10.1016/S0040-4039(00)73081-4

中图分类号：

O62 [有机化学];

学科分类号：

070303 ; 081704 ;

摘要：

The stable carbocation, tri(2-methyl-1-azulenyl)methyl hexafluorophosphate (2) was prepared. Steric effect of three 2-methyl groups was investigated by comparison with the 3,3',3''-trimethyl analogue, tri(3-methyl-1-azulenyl)methyl cation (1). Dynamic stereochemistry of 2 was studied by temperature dependent H-1 NMR spectra, which were analyzed by flip mechanism. The threshold rotational mechanism for 2 was a two-ring flip in contrast to a one-ring flip for 1, and the activation energies for 2 (18.6 and 17.5 kcal/mol) were higher than for 1 due to increased crowding in the transition state for the rotation.

引用

页码：3723 / 3726

页数：4

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