Thiosemicarbazides formation

Br , citrate, CE, CN , E, NH3, SCN , S20 , thiourea, thioglycolic acid, diethyldithiocarba-mate, thiosemicarbazide, bis(2-hydroxyethyl)dithiocarbamate Acetate, acetylacetone, BE4, citrate, C20 , EDTA, E , formate, 8-hydroxyquinoline-5-sul-fonic acid, mannitol, 2,3-mercaptopropanol, OH , salicylate, sulfosalicylate, tartrate, triethanolamine, tiron... 

Acetone, (reduction with) ascorbic acid, citrate, CE, CN , 2,3-dimercaptopropan-I-oI, EDTA, formate, E, 8CN , 80 , tartrate, thiosemicarbazide, thiourea, triethanolamine CE, EDTA, F , 8CN , tartrate, thiourea, triethanolamine Citrate, CN , 8CN , tartrate, thiourea Citrate, EDTA, F , oxalate, tartrate, tiron... 

Li and co-workers introduced a rapid and efficient microwave-assisted method to prepare new disubstituted 1,3,4-thiazoles from 1,4-disubtituted thiosemicarbazides with the objective to obtain biologically active molecules. The intermediate l-aryloxyacetyl-4-(4-methoxybenzoyl)thiosemicarbazide was irradiated in an excess of glacial acetic acid in a domestic microwave oven and led to the formation of 2-(methoxybenzoyl-5-aryloxymethyl)-l,3,4-dithiazoles in good yields [30] (Scheme 20). 

A similar approach via desulfurization of the thiosemicarbazide-substituted pyrimidone 290 using 4-nitrobenzyl bromide leads to efficient formation of the tricyclic system 291 in excellent yield (Equation 79) <2000RJ0430>. 

Jain and Handa reported [82IJC(B)732] that the mode of ring closure may depend critically on the 5-substituent of the triazole. 3-Mercapto-5-(4 -pyridyl)[l,2,4]triazole 143 was reacted with phenacyl bromides to give 144, which on treatment with PPA resulted in the formation of thiazolo[2,3-c][l,3,4]triazoles 145. The structure of 145 [R = (4-Cl)C6H4] was proved by an independent synthesis starting with isonicotinyl thiosemicarbazide. 

Formation of 123-125 are explained by formation of the neutral adduct 127, a tetracyanoethane derivative, from the starting 4-substituted thiosemicarbazides 121a-c and 122. Elimination of one molecule of HCN afforded the intermediate 128, which cyclized to the thiadiazepine derivatives 123a and 123b. 

Phenylamino-l,2,3,4-thiatriazole 87 in principle can be prepared by heating of isomeric l-phenyltetrazole-5-thiol 170 (Equation 18) <1967JOC3580>. The formation of the thiatriazole 87 is accompanied by significant formation of phenylaminonitrile. Therefore, we recommend the use of other synthetic methods (see Section 6.09.8), for instance, the nitrosation of 4-phenyl-3-thiosemicarbazide < 1971JIC843, 1981JIG1087 >. 

The procedure is essentially similar to that described for the preparation of 5-amino-l,2,3,4-thiatriazole. Freund and Hempel6,7 have reported observing that the initial diazotization products of 4-aryl-substituted thiosemicarba-zides lead to the formation of tetrazoles, while the corresponding 4-alkyl-substituted thiosemicarbazides were considered by Freund and Schwarz8 to be thiatriazoles. However, Oliveri-Mandala,9 on the basis of his study of the reaction of alkyl and aryl isothiocyanates with hydrazoic acid, concluded that the initial diazotization product of either 4-aryl or 4-alkyl thiosemicarbazides were open-chain thiocarbamyl azides, RNHC( S)N3. Lieber, Pillai, and Hites10 have recently clarified this situation and have shown... 

The reaction between Ph2SnCl2 and thiosemicarbazide using acetone-ethanol as a solvent mixture resulted in the formation of bis(acetone thiosemicarbazone-S)dichlorodiphenyltin. In the monomeric hexacoordinate complex, each of the two monodentate ligands coordinate to the tin atom through the sulfur atom to form a distorted-octahedral geometry (the S —Sn bond length is 2.712 A)1122. 

Cyclization in phosphorus oxychloride of semicarbazides (79 X = NHR) yields aminooxadiazoles (81) whereas thermolysis leads to loss of ammonia (when X = NH2) and formation of an oxadiazolinone (80). Cyclization to aminooxadiazoles (81) occurs when thiosemicarbazides (82) are heated with an oxidizing agent such as lead oxide. This reaction has been widely applied to the synthesis of aminooxadiazoles, sometimes in low yields, and has been used to prepare 2-amino-l,3,4-oxadiazole (81 R1 =R2 = H). 5-Methyl ethers of thiosemicarbazides (82) cyclize, with loss of methanethiol, to aminooxadiazoles (81) on heating, but in PPA cyclization to 2-methylthio-l,3,4-oxadiazoles occurs. 

The synthesis of 1,3,4-thiadiazoIes is discussed in terms of the number of bonds being formed and by ring transformation. Thiadiazole synthesis by one-bond formation is exemplified by the cyclization of an acylated thiosemicarbazide as shown in Scheme 16. The most common two bond formation takes place via 1,3-dipolar cycloadditions presented in Scheme 23. 

Reaction of l,3-benzoxazin-4-ones (43, 44) or trithioisatoic anhydride (45) with amidrazones (46, 47) or thiosemicarbazide (48) resulted in the formation of 3-(l-amidino)- (49-51) and 3-(l-thioureido)pyrimidines (52) respectively. Compounds 49-52 underwent thermal intramolecular cyclization to the corresponding l,2,4-triazolo[l,5-c]quinazolines (53-56) [68CB2106 76MI1 80PHA582 83MI1 85H(23)2357] (Scheme 18). 

Willems, J. F. Formation of Heterocyclic Nitrogen Containing Thioxo Compounds with Thiosemicarbazides.147... 

By analogy with what is known for thiosemicarbazide, cyclizations of thiocarbohydrazide (47) could be expected to lead to hydrazino-thiadiazoles. However, a much stronger tendency toward formation of triazoles is apparent in the latter case, and thiadiazoles are formed only in special reactions. Thus 1-thiocarbamoylthiocarbohydrazide... 

The formation of alternative heterocycles can be the main reaction with semicarbazides or thiosemicarbazides which are used extensively in the preparations of triazolinones and triazolinethiones. Aminoguanidines can give rise to isomeric triazoles. The preferred formation of thiadiazole (157) from the 1-acylthiosemicarbazide (Scheme 66) is explained by the protonation of N-4 in strong acid with accompanying loss of nucleophilicity, while in the presence of base its nucleophilic character is enhanced 73JOC3947) and (158) is obtained. 

The formation of oxadiazole (159) or triazole (160) from the thiosemicarbazide (161) under different conditions of methylation in the presence of base (Scheme 67) is less readily explained (71MI41200). Relative rates of methylation on S and O are involved but the different temperatures make a direct comparison impossible. The effect of acidity cannot be neglected as shown in Scheme 68 (63CB1059). 

The highly levorotatory y-hexaacetate would have to be a structural isomer of the two anomeric a and /3 hexaacetates. It was pointed out that the aldehyde structure XLIII was improbable from the mode of its formation moreover it was excluded by the fact that the compound failed to give rise, on treatment with thiosemicarbazide, to the ultraviolet absorption band at 2700 A characteristic of tiuosemicarbazones. Since ring isomerism in the N-methyl-L-glucosamine portion or a 1,3-orthoacetate structure did not seem probable, the 1,6-furanose structure (XLIV) was tentatively proposed for this compound. 

Oxystarch reacted with phenylhydrazine to give a yellow compound" " which contained one basic group per dialdehyde unit." Similar reactions were found with isonicotinoylhydrazine, thiosemicarbazide, and p-aminobenzaldehyde thiosemicarbazone. Structures of the general type (97) were assigned to these polymers." That this structure is incorrect for the phenylhydrazine derivative was shown by its formation of a poly(di-phenylformazan). Mester therefore suggested structure (104) for the... 

Little is known about the mode of action of hydra-zinecarboxamide-derived fungicides. Since diazene formation is involved in the fungitoxic action of phenyl-thiosemicarbazide (2 2) and is implicated in a glutathione-oxidation mechanism to account for fungi-toxicity of similarly structured compounds (2 1 ), it is conceivable that diazenes described in this study may well play a critical role in the action of fluorine-substituted hydrazinecarboxamide fungicides and perhaps larvicides as well. 

Addition to the Carbonyl Group — The internal, cyclic hemiacetal formation is one of the illustrations of such addition. The H2N-X nucleophiles, with X being NH2 (hydrazine), NHAr (arylhydrazines), OH (hydroxylamine), NHCONH2 (semi-carbazide), NHCSNH2 (thiosemicarbazide), or alkyl (primary amine), produce hydrazones, arylhydrazones, oximes, semicarbazones, thiosemicarbazones, and alkyl imines (Schiff bases), respectively, following the following path 5.4 + 5.15 — 5.16 ->. .. -> 5.21. 

In view of its zinc content, the activity of yeast ADH was studied in the presence of a large variety of agents known to combine with this metal ioii in simple systems as salts, chelates, or complex ions. It was expected that the formation of such compounds would reduce the activity of the enzyme if zinc were involved in its mechanism of action. In addition to OP, aa D, 8-OHQ-5SA, DZ, and TU (Vallee and Hoch, 1955), the following have since been found to inhibit yeast ADH activity NaDDC, BAL, Cupferron, thiosemicarbazide, sodium sulfide, potassium cyanide, and sodium azide (Vallee and Hoch, in preparation for publication). Inhibition was found to be strongly dependent upon the time of contact between the enzyme and the inhibitor prior to the measurement of activity, the pH of the preincubation mixture, and the temperature at which the preincubation was allowed to take place. 

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