Mercapto-substituted 1,2,4-triazoles are very interesting compounds as they play an important role in chemopreventive and chemotherapeutic effects on cancer. In recent decades, literature has been enriched with sulfur- and nitrogen-containing heterocycles which are used as a basic nucleus of different heterocyclic compounds with various biological applications in medicine and also occupy a huge part of natural products. Therefore, we shed, herein, more light on the synthesis of this interesting class and its application as a biologically active moiety. They might also be suitable as antiviral and anti-infective drugs.

Symmetrically and unsymmetrically N¹,N²-disubstituted hydrazine-1,2-dicarbothioamides (2,5-dithiobiureas) react with dimethyl acetylenedicarboxylate in refluxing ethanol to give dimethyl 2,2′-[2,2′-(hydrazine-1,2-diylidene)bis(3-aryl/alkyl-4-oxothiazolidine-5,2-diylidene)diacetate and methyl 2-(2-{[5-(2-methoxy-2-oxoethylidene)-4-oxothiazolidin-2-ylidene]hydrazono}-4-oxothiazolidin-5-ylidene)acetate derivatives and N²,N⁵-disubstituted 1,3,4-thiadiazole-2,5-diamines. The structure of one product has been confirmed by a single-crystal X-ray structure analysis. A rationale for the formation of the products is presented.

An efficient route for the synthesis of oxa-aza- and bis-oxa­thiaaza[3.3.3]propellanes via reactions of symmetrical and unsym­metrical N¹,N²-disubstituted hydrazine-1,2-dicarbothioamides (2,5-dithiobiureas) with (1,3-dioxo-2,3-dihydro-1H-inden-2-ylidene)propanedinitrile in tetrahydrofuran is described. The rationale behind these conversions involving nucleophilic addition on the dicyanomethylene carbon atom is presented. The structures of these unusual products are confirmed by X-ray crystal structure analysis.

The coupling reaction between N-substituted (E)-hex-2-en-ylidene hydrazinecarbothioamides and 2,3-dichloro-1,4-naphthoquinone affords substituted amino-5-pentenyl-naphtho[2,3-f]-1,3,4-thiadiazepine-6,11-diones and 2-(substituted amino)naphtho[2,3-d]thiazole-4,9-diones. These conversions can be rationalized by proposing a nucleophilic addition to C2 and C3 of dichloro-1,4-naphthoquinone. The structure of one of the products was confirmed by single-crystal X-ray analysis.

The reactions of dialkyl acetylenedicarboxylates with various 2-oxo-acenaphthoquinylidene- and 4-acetyl[2.2]paracyclophanylidene-thiosemicarbazones were investigated. Using simple experimental procedures, 1,3-Thiazolidin-4-ones derived from acenaphthequinone or [2.2]paracyclophane were obtained as major products in good yields. In the case of allyl derivative of acenaphthoquinylidene-thiosemicarbazones, a complex structure of tetramethyl 5-(2-(((Z,E)-N-allyl-N′-(2-oxoacenaphthylen-1(2H)-ylidene)carbamohydrazonoyl)thio)-1,2,3-tris-(methoxycarbonyl)-cyclopropyl)-4-methoxy-7-oxabicyclo[2.2.1]hepta-2,5-diene-1,2,3,6-tetracarboxylate was formed. Single crystal X-ray analysis was used as an efficient tool to confirm the structure of the synthesized compounds as well as different spectroscopic data (¹H-NMR, ¹³C-NMR, 2D-NMR, mass spectrometry and elemental analysis). The mechanism of the obtained products was discussed.