Thiocarbazides

Diaryl carbazides and thiocarbazides, e.g., 43, can be oxidized at alkaline pH to yield C-hydroxy or C-mercapto formazans (44) (Eq. 8).68,129 The replacement of C-halo formazans is considered to be a better method60 for the preparation of 44. A class of cyclic formazans (45) can be obtained by air oxidation of amidrazones (46) (Eq. 9) 9,73,101,102 jhough this is formally a formazan, there are no reports of its oxidation reactions. In a... 

The explosive title compound was not isolated after preparation from thiocarbazide and nitrous acid, but was condensed with various ketones to give the hydrazones. 

The key intermediate in these transformations was the hydrazide 83 obtained from the ester 82 by simple treatment with hydrazine hydrate. This intermediate was then transformed by aldehydes, sulfonic chlorides, and isothiocyanates to obtain various aryl hydrazones 84, sulfonylhydrazines 85, and thiocarbazides 86. 

Sulphur and selenium donor ligands. The reaction between AgNOj and the series of thiocarbazide derivatives RCONHNHC(S)NHNH2 (R == Me, Ph, or C6H4N) has produced white diamagnetic solids for which the polymeric structures (94) are proposed. Support for these structures comes from their low solubility, and i.r. data suggesting terdentate co-ordination via the terminal N, the amido N, and the S atom. The Ag ion attains its usual co-ordination... 

The precipitate is almost pure white. More diphenyl-thiocarbazide crystallizes from the red alcoholic filtrate and washings, if they are allowed to evaporate slowly. When the mixture is allowed to stand for some time before it is filtered, the amount of precipitate is increased and that of the material left in the filtrate is decreased. 

The rather unstable 5-hydrazino-l,2,3,4-thiatriazole 87 (R = NH2) can be prepared by reaction of thiocarbazide with nitrous acid at 0°C in moderate yield <1985ZC136, 1989JPR115>. 

Tellurium(IV) reacts with thiourea, S=C(NH2)2, (whose concentration in the final solution should be -10%) in 1 M H2SO4, HNO3, or H3PO4 to form a yellow cationic complex suitable for spectrophotometry [36]. The absorption maximum of the complex occurs at 320 nm. The cationic complex of tellurium with thiourea can be extracted with TBP as the ion-associate with thiocyanate ions. The following thiourea derivatives have been proposed for the spectrophotometric determination of tellurium l,4diphenylthiosemicarbazide [37], diphenyl-thiocarbazide, dinaphthylthiourea, and tetramethylthiourea [38]. 

A major route to 2-amino-6/f-l,3,4-thiadiazines is by the condensation of a-haloketones with thiosemicarbazides (Section 6.17.7.2.2(ii)). Replacement of the thiosemicarbazide by a thiocarbamic acid or by a thiocarbazide results in formation of 3,6-dihydro-2//-l,3,4-thiadiazin-2-ones. Likewise, replacement with an A -arylthiohydrazide yields a 4//-l,3,4-thiadiazin-5(6/f)-one (Section 6.17.7.2.2(ii)). 3,6-Dihydro-27/-thiadiazin-2-ones are also available by the condensation of alkyl-hydrazines with a-(methoxycarbonylsulfenyl)alkylaryl ketones (Section 6.17.7.2.2(vi)), while the ring closure of (arylhydrazonoalkylthio)acetic acids with dicyclohexylcarbodiimide provides an alternative route to 4 -l,3,4-thiadiazin-5(677)-ones (Section 6.17.7.1.2). 2-Phenylimino-3-aryl-2,3-dihydro-l,3,5-thiadiazin-6-ones result from treatment of a-hydrazono-j8-ketoesters with aryl-isothiocyanates (Section 6.17.7.2.2(iv)). 

Table 2. Chalcogenide Precursors. TU thiourea, TA thioacetamide, TC thiocarbazide, TSC thio-semicarbazide, ETU ethylthiourea, ATU allylthiourea, SU selenourea, DSU N,N dimethyl selenourea, TS thiosulfate, SES selenonilfate...

Dithiadiazines. (1) Oxidative cyclization of l,6-diphenyl-2,5-dithiobiurea (Equation 14) (2) oxidative cyclization of A, A -dicarbethoxy-A, A -bis(mercaptomethyl)hydrazine (Scheme 32) (3) condensation of an oxamic acid thiocarbazide with chlorocarbonylsulfenyl chloride (Equation 21) (4) condensation of thiosemicarbazide derivatives with A -phenyl-3 -chloroisothiocarbamoyl chloride (Equation 22). Method (4) is the most general of these, provides good yields, and precursors are reasonably accessible. 

It is possible that the interference by molybdate ions can by averted through their reaction with thiocarbazide. At pH 2 there results a brown precipitate which can be extracted by a mixture (1 2) of acetone and n-butanol. Tungstate ions are not altered by this treatment. ... 

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