Synthesis of cycloalkenopyrylium salts
Acylation of cyclopentylidenecyclopentanone, cyclohexenylcyclohexanone, and cycloneptenylcycloheptanone with anhydrides of aliphatic acids in the presence of 70% perchloric acid is studied. A simple method of synthesis of 2-alkyl-3, 4; 5, 6-bicycloalkenopyrylium salts is given. Treatment of the pyrylium salts with ammonia gives 2-alkyl-3, 4; 5, 6-bicyclopenteno- and cycloheptenopyridine in good yields.