In the last few years we have been involved in a programme aimed for exploring potential utilities of thiazolidinones in heterocyclic syntheses. During this phase of our research we reported on condensation reactions of thiazolidinones with nu~leophiles'-~). In conjunction with this work we report here on reactions of thiazolidinones with a nucleophile that leads to ring cleavage.
The reaction of 5-phenylhydrazono-2-thioxo4thiazolidinone (1) with hydrazine hydrate affords a product CgHgNsS2. Structure 3 was suggested for this product. Its 'H-NMR spectrum showes 9 H, two singlets at 6 13.3 and 13.5 (2 NH) besides a multiplet at 6 6.7-7.4 corresponding to 7 H (5H, arom. + 2H, NH, SH). The formation of 3 is assumed to proceed via the cyclization of C(a-phenylhydrazono-mercaptoacetyl)thiosemicarbazide (2). The formation of the 4-( 1 -phenylhydrazono-1 -mercaptomethyl)-1,2,4-triazol-4-ine-3-thione (3) or tautomers like 3a via the reaction of 1 with hydrazine hydrate finds parallelism to the formation of 1,2,4-triazoles from reaction of substituted rhodanines with hydrazine hydrate under similar condition^^'^).
Refluxing of 3 with formaldehyde or benzaldehyde in absol. ethanol gave the new fused thiazolo[4,3-c]triales 4a and b. Heating of 3 with acetone gave 4c. The structures of 4a-c were deduced from elemental and spectral data.
3 reacted with phenacyl bromide in the presence of triethylamine to give the thiazolo[5,4-c]thiazine 5.
Treatment of 3 with acetic anhydride affords the diacetyl derivative 6.
Biological Results
Results of antimicrobial activity tests are shown in Table