SYNTHESIS OF DIPOLAR ETHYLENEIMIDAZOLIUM BENZIMIDAZOLATE INNER SALTS AND THEIR TRANSFORMATION TO 2-VINYLBENZIMIDAZOLES THROUGH A TYPE OF BETA-ELIMINATION REACTION

The synthesis and spectroscopic properties of the fairly stable title inner salts (5) are reported. For several of the betaines (5), both th e highly dipolar character due to the terminal rings and the nature of the spacer promoted a type of beta-elimination reaction. Thus, format ion of 2-vinylbenzimidazoles (7) from the corresponding betaines (5) p roceeds in high yield under neutral and mild conditions. Following sim ilar treatment, the 1-(2-benzimidazol-2-ylethyl)imidazolium salt (8b) undergo nucleophilic substitution reactions.