FEATURES OF REACTIONS OF QUATERNARY SALTS DERIVED FROM (4<i>Z</i>)-5-(BROMOMETHYL)-2,2,6,6-TETRAMETHYLHEPT-4-EN-3-ONE. SYNTHESIS OF AZOLO[<i>a</i>]AZEPINE AND INDOLIZINE DERIVATIVES

Abstract

The alkylation of 1-alkyl-2-methyl-1H-imidazoles, 1,2-dimethyl-1H-benzimidazole, and 2-R-pyridines by (4Z)-5-(bromomethyl)-2,2,6,6-tetramethylhept-4-en-3-one gives 1-alkyl-3-[(2Z)-2-tert-butyl-5,5-di-methyl-4-oxohex-2-en-1-yl]-2-methyl-1H-imidazol-3-ium, -1H-benzimidazol-3-ium, and 2-R-pyridinium bromides. Heating solutions of these diazolium salts in ethanol with potassium carbonate leads to 1,5-dihydroimidazo[1,2-a]azepinium and 5,10-dihydroazepino[1,2-a]benzimidazolium derivatives, while heating the pyridinium salts with triethylamine leads to indolizine derivatives. Heating solutions of quaternary salts derived from 1,2-dimethyl-1H-imidazole and 2-methylpyridine in acetic anhydride gives allylic rearrangement products, namely, 3-[(2Z)-2-tert-butyl-5,5-dimethyl-4-oxohex-1-en-1-yl]-1,2-dimethyl-1H-imidazol-3-ium and -2-methylpyridinium bromides, which under the action of base (MeONa for the diazolium salt and Et₃N for the pyridinium salt) are converted into 1,5-dihydroimid-azo[1,2-a]azepinium and indolizine derivatives, respectively.

Authors: L. M. Potikha, A. R. Turelik, and V. A. Kovtunenko.

English translation in Chemistry of Heterocyclic Compounds, 2012, 48 (2), pp 334-342

http://link.springer.com/article/10.1007/s10593-012-0994-2