Syntheses of Azulene Analogues of Triphenylmethyl Cation: Extremely Stable Hydrocarbon Carbocations and the First Example of a One-Ring Flip as the Threshold Rotation Mechanism for Molecular Propellers
作者:Shunji Ito、Noboru Morita、Toyonobu Asao
DOI:10.1246/bcsj.68.1409
日期:1995.5
A series of azulene analogues of triphenylmethyl cation (tri(1-azulenyl)methyl, di(1-azulenyl)phenylmethyl, and (1-azulenyl)diphenylmethyl hexafluorophosphates) were synthesized by hydride abstraction from the corresponding methane derivatives with DDQ. In order to examine the effect of substituents on the cations, and to enhance their stabilities, a series of cations bearing 3-methyl, 3-methoxycarbonyl
ipso-substitution reactions between 1,3,6-tri-tert-butylazulene (2) and several electrophilic reagents were examined. Friedel–Crafts and Vilsmeier reactions of 2 gave the corresponding ipso-substitution products in moderate to excellent yields. One of the ipso-substitution products, 1,6-di-tert-butyl-3-formylazulene (5), was converted in high yield into the synthetically more useful azulene derivative