ON THE REACTION OF NITRILIUM SALTS WITH HETEROCYCLIC NITRONES

Nitrilium hexachloroantimonates 1a-c reactwith pyridine N-oxides 2a, d , f, j, m, o to afford bicyclic 2,3-dihydropyridinium salts 5a-p. The constitution of 5f was secured by an X-ray crystallographic analysis. Compounds 5 proved to be thermally labile (23-82 degrees C) rearrangin g to 2-acylamino- pyridinium salts 6a, f-i or decomposing to tars. The benzimidazole-3-oxide 7 reacts with nitrilium salts 1a, b to 2-acylam inobenzimidazoles 9a, b. The experimental results as well as AM1 calcu lations support a mechanism for the reaction of nitrilium cations with heterocyclic nitrones, which has originally been suggested by Abramov itch [25, 26].