Preparation of New Nitrogen-Bridged Heterocycles 72. A New Approach to 1-Acyl-3-(substituted methylthio)thieno[3',4':4,5]imidazo[1,5-a]pyridine Derivatives
corresponding thieno[3',4':4,5]imidazo[1,2-a]pyridine derivatives in low to moderate yields via the intramolecularcyclization of the resulting 1,5-dipoles followed by the aromatization of the primary cycloadducts. Interestingly, the reactions using unsymmetrical 3-amino-4-[1-(3-methylpyridinio)]thiophene-5-thiolates afforded only 8-methylthieno[3',4':4,5]imidazo[1,2-a]pyridines and the other 6-methyl derivatives