Abstract
A set of 2-substituted 1-(9,10-dihydroacridin-9-ylidene) thiosemicarbazides 4a-d (H, methyl, ethyl, and n-butyl substituents) were treated with dimethyl acetylenedicarboxylate (DMAD) to yield 5-membered ring 1,3-thiazolidin-4-one products 5a-d. The methyl derivative 4b, upon reaction with methyl propiolate (MP), yielded a 6-membered thiazin-4-one ring product 7b. The structures of the methyl derivative products 5b and 7b were conclusively proven by NMR examinations and compared to X-ray crystallographic analysis. The ring-chain tautomerism of the thiosemicarbazides, the regio- and stereoselectivity of the reactions, the adopted s-cis conformations of the Z configurations of the products, and the prototropic tautomerism of all the compounds were all substantiated.
Published Version
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