Abstract
On reaction with sodium salts of such active methylene compounds as ethyl cyanoacetate, malononitrile, ethyl malonate and phenylacetonitrile, thiazolo [3, 2-b] pyridazinium perchlorates (I) furnish anhydro-8-(α, α-disubstituted methylene)-5, 8-dihydrothiazolo [3, 2-b]-pyridazinium hydroxides (IV, V, VI, and VII). On treatment with sodium hydrosulfide as a nucleophile, I affords anhydro-8-mercaptothiazolo [3, 2-b] pyridazinium hydroxide (X). The reaction is initiated by the nucleophilic addition of the reagents at the 8-position, and subsequent oxidation by atmospheric oxygen via radical intermediates gives rise to the ylide compounds.
