Dehydrohalogenation of isomeric 2- and 3-bromomethyl substituted 2,3-dihydrooxazolo[3,2-a]pyridines

3-(Bromomethyl)dihydrooxazolo[3,2-a]pyridinium bromide under the action of base gives stable non-aromatic methylidene structure which can be converted into aromatic oxazolopyridinium cation only under the action of a superacid. On the contrary, 2-bromomethyl isomer under the same conditions affords only aromatic cation. The structure of the products was confirmed by X-ray diffraction.