Tris(3,6-di-t-butyl-1-azulenyl)methyl cation; hydrocarbon cation with the highest pKR+ value

Abstract

Tris(3,6-di-t-butyl-1-azulenyl)methyl (5), tri(3-t-butyl-1-azulenyl)methyl (10), and tri(6-t-butyl-1-azulenyl)methyl (11) hexafluorophosphates were synthesized. Their pKR+ values were determined as 14.3, 13.2, and 13.7, respectively, and the value of 5 showed the highest one as carbocation ever reported. The extreme stability of methyl cation 5 is mainly attributable to steric effects of six bulky t-butyl groups in addition to the contribution of dipolar structure of three azulene rings. © 1994.