| Abstract: | When 3-chloro-4,5-diaminopyridazine ( 2 ) was treated with sodium methylmercaptide in refluxing N,N-dimethylformamide, two heterocycles were formed and isolated, neither of which was the expected 3-methylthio-4,5-diaminopyridazine ( 3 ). A thorough spectral analysis of these heterocycles showed them to be 4-methylthioimidazo4,5-d]pyridazine ( 5 ) and imidazo4,5-d]pyridazine-4-thione ( 6 ). N,N-Dimethylformamide was found to provide the one carbon unit required for the formation of 5. The origin of 6 was shown to be a result of S-demethylation of 5. S-Demethylation of 3 could also be effected with sodium methylmercaptide in methyl sulfoxide without the occurrence of annulation. In methyl sulfoxide the process of demethylation was accelerated and occurred at lower temperature. |
