Thio thiosemicarbazones

Semicarbazones and thio-semicarbazones C=N— NH2 f 0 (or S) 1665-1642 (vs) 1620-1610 (vs) Aliphatic. Thiosemicarbazones fall in lower end of range. Aromatic derivatives... 

The thiophene analog of chloramphenicol (255) has been synthesized,as also have been similar structures. The antibacterial activity of all was much lower than that of the natural antibiotic. The thioamide of 2-thenoic acid has been prepared in a study of potential antitubercular compounds. It did not surpass thioisonico-tinamide in antitubercular activity. The thiosemicarbazones of thio-phenealdehydes and ketones (cf. Section VII,D) show high activity against Mycobacterium tuberculosis, but are very toxic. The thiosemi-carbazone of 4-(2-thienyl)-3-buten-2-one has been reported to be capable of completely inhibiting the in vitro growth of M. tuberculosis even in relatively low concentrations. ... 

Since the causative organism of leprosy, one of the world s six major diseases, Mycobacterium leprae, is closely related to Mycobacterium tuberculosis, thio-semicarbazones have also been used as second-line drugs in the chemotherapy of leprosy [38]. The most widely used in leprosy treatment has been thiacetazone, and structure-activity relationships for it are similar to those observed for antitubercular thiosemicarbazones [39, 40]. 

A more convenient method for the preparation of this ring system started with thiosemicarbazone 123, whose alkaline cyclization to 2-thio-5-(o-nitrobenzyl)-6-azauracil 125 proceeds smoothly (84CCC2628). In contrast to the above method, it is not necessary to isolate the Z-form of thiosemi-... 

Many organic spectrophotometric reagents for Pd incorporate sulphur as a ligand atom. Apart from dithizone and thio-Michler s ketone, which have been discussed above, examples include the thiourea derivatives [33-36] p-dimethylaminobenzylidene-rhodanine (rhodanine) (e = 4.9 10 ) [37] and its derivatives [38], thiodibenzoylmethane [39,40], and thiosemicarbazone derivatives [41—47]. 

A number of other ring systems have been prepared by intramolecular bis-annulation procedures (Scheme 15). The pyrrolothiadiazole (88) <89H(29)133> and the benz fused analogue (89) <85LA1679> were prepared by treatment of thiosemicarbazone derivatives with acetic anhydride. Thio-semicarbazone (90) similarly underwent a double cyclization to give the pyrrolotriazoline (91)... 

This reaction was first reported by Hantzsch and Weber in 1887. It is the formation of thiazole derivatives by means of condensation of a-haloketones (or aldehydes) and thioamides. Therefore, it is generally known as the Hantzsch thiazole synthesis. In addition, other names, including the Hantzsch synthesis, Hantzsch reaction, and Hantzsch thiazole reaction are also used from time to time. Besides thioamides, other thio-ketone derivatives such as thiourea, dithiocarbamates, and ketone thiosemicarbazone can also condense with a-halo ketones (or aldehydes) to form thiazoles. This reaction occurs because of the strong nucleophilicity of the sulfur atom in thioamides or thioureas, and normally gives excellent yields for simple thiazoles but low yields for some substituted thiazoles, as of dehalogenation. This reaction has been proven to be a multistep reaction, and the intermediates have been isolated at low temperatures, in which the dehydration of cyclic intermediates seems to be the slow step. It is found that a variety of reaction conditions might result in the racemized thiazoles that contain an enolizable proton at their chiral center, and it is the intermediate not the final product that is involved in the racemization. Therefore, some modifications have been made to reduce or even eliminate the epimeriza-tion upon thiazole formation. In addition, this reaction has been modified using a-tosyloxy ketones to replace a-haloketones. ... 

The a-(AO-heterocycIic carboxaldehyde thiosemicarbazones constitute a class of agents which possess both antineoplastic and antiviral activity [1], The first agent of this series to be examined for biological activity, 2-formylpyridine thio-... 

Oxidation of 4-acetoxy-l-methylisoquinoline (76) with selenium dioxide produced the corresponding 1-carboxaldehyde, which upon acid hydrolysis yielded the 4-hydroxy derivative. Treatment of heterocyclic aldehydes with thio-semicarbazide produced the desired thiosemicarbazones. In general, the 4-substituted derivatives were less effective than (1) as antineoplastic agents against Sarcoma 180 ascites cells in mice however, the sodium salt of the 4-hydroxy derivative was considerably more efficacious than (1) against the L-1210 lymphoma. 

DL-showdomycin from teloidinone (Scheme 18), and of racemic carbocyclic analogues of 6-azapseudouridine, 2-thio-6-azapseudouridine, and pyrazofurin by way of cyclization of the syn and anti-semicarbazones, thiosemicarbazones, and ethoxycarbonylmethylhydrazones, respectively, of a cyclopentylglyoxylate derivative (Scheme 19). ... 

The barrier to rotation about the C—N bond for 1,1-dimethylselenosemi-carbazide appeared to be slightly higher than that found for its thio-analogue (AF"=11.6 and 11.2kcalmor, respectively) Other papers report on the influence of the substituents R and X on the barrier to rotation of the dimethylamino-group in the pyrazoles (528) the determination of AP (21.1 kcal mol ) for the restricted rotation around the CS—bond in the thiophosphinoylthioformhydrazide (529), and the syn-anti isomerism of isatin /3-thiosemicarbazones. ... 

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