Synthesis of Pyridazine Derivatives with Sulfur-Containing Substituent. III. Two Types of Cyclizations in the Concurrent Formation of 1, 6-and 1, 9-Disubstituteddipyridazo [4, 5-b : 4', 5'-e]-1, 4-dithiin Derivatives. (2)

抄録

4, 5-Dimercapto-3 (2H)-pyridazinones (7, 8, 9), 3, 4-dichloropyridazine-5-thiol (11), which must have been produced during the debenzylation reaction of 3, 4-dichloro-5-benzylthiopyridazine (10), and 4-chloro-5-mercapto-3 (2H)-pyridazinethiones (13, 14) furnished the concurrent formation of the corresponding pairs of dipyridazo [4, 5-b : 4', 5'-e]-1, 4-dithiin derivatives, respectively. On the other hand, 3-methylthio- (15) and 3-morpholino-4-chloropyridazine-5-thiol (16) formed the corresponding 1, 6-disubstituted dipyridazo [4, 5-b : 4', 5'-e]-1, 4-dithiin alone, however, 3-methylthio- (17) and 3-morpholinopyridazine-4, 5-dithiol (18) concurrently formed the corresponding pairs of 1, 6- and 1, 9-disubstituted derivatives. For the interpretation of these reactions, the formation mode was proposed to be divided in two classes according to the characters of the thioketo carbene species as active intermediates. The former reactions proceed through the corresponding thioketo carbene species which is so reversibly interconvertible, that subsequently dimerizes per se in 1, 3-dipolar fashion to concurrently form a pair of the corresponding derivatives. The latter reactions also proceed through the relevant thioketo carbene species in the same fashion of dimerization as described in the former reactions, however, existence of any reversible interconversion between the counterpart one is scarcely infered. So the relevant carbene species of the cyclization started with 15 and 16, independently exist as a pair in a definite mixing proportion, subsequently they combine by the two dimerization mode.