A Facile Synthesis of Oxoindenothiazine and Dioxospiro(indene-2,4′-thiazine) Derivatives from (Substituted ethylidene)hydrazinecarbothioamides

(E)-2-[2-(1-Substituted ethylidene)hydrazinyl]-5-oxo-9b-hydroxy-5,9b-dihydroindeno[1,2-d][1,3]-thiazine-4-carbonitriles and (E)-5-oxo-[(E)-(1-substituted ethylidene)hydrazinyl]-2,5-dihydroindeno[1,2-d][1,3]thiazine-4-carbonitriles have been obtained from the reaction of 2-(substituted ethylidene)hydrazinecarbothioamides with 2-(1,3-dioxo-2,3-dihydro-1H-inden-2-ylidene)propanedinitrile (1) in ethyl acetate solution. However, (Z)-6′-amino-1,3-dioxo-3′-substituted-2′-[(E)-(1-phenylethylidene)hydrazono]-1,2′,3,3′-tetrahydrospiro(indene-2,4′-[1,3]thiazine)-5′-carbonitriles were observed during the reaction of N-substituted-2-(1-phenylethylidene)hydrazinecarbothioamides with (1). The structure assignment of products has been confirmed on the basis of 1H-, 13C-NMR, and mass spectrometry, as well as theoretical calculations.