1,4-Diphenyl-3-thiosemicarbazide

In the early investigation of the nitrosation of 1,4-diphenyl-thiosemicarbazide (279, R = R = Ph), the product was obtained as deep red needles, m.p. 110°, and was allocated the remarkable 1,3-endoxyhydrazomethylene structure (280). Treatment of this deep red compound with warm aqueous alkali gave a colorless isomer, m.p. 157°, which was formulated as having one of the equally unacceptable structures 281 or 282. Recent investigations have established that nitrosation of 1,4-diarylthiosemicarbazides (279) yield the meso-ionic 1,2,3,4-oxatriazol-5-imines (277), which are transformed by base into the meso-ionic isomers (278). These alkaline transformation products formulated as meso-ionic l,2,3,4-tetrazol-5-ones (278) are in fact identical (see Section VII, J, 1) with substances prepared, but not formulated, by von Pechmann many years ago. ... 

The condensation products (1 1) of pentane-2,4-dione and 1,3-diphenyl-propane-1,3-dione with thiosemicarbazide, 4-methylthiosemicarbazide, and aminoguanidinium nitrate were formed (86KGS128 87ZOB584 90-KGS1260) as the cyclic isomers 78, which sometimes readily underwent dehydration to the corresponding pyrazoles. 

L = diphenyl-(o-diphenylarsinophenyl)phosphine SN = l,2-bis-(o-aminophenylthio)ethane NS = thiosemicarbazide PS = 2-diethylphosphinoethyI-l-thioethane... 

From the reaction of 6-p-chlorostyryl-3-thioxo-3,4-dihydro-l,2,4-triazin-5(2F/)-one (271) with phenylmagnesium bromide a mixture of seven products was isolated. These were separated and identified as 6-/ -chlorostyryl-5-phenyl-l,2,4-triazine-3(2/f)-thione (272), 6-p-chlorostyryl-5,5-diphenyl-4,5-dihydro-l,2,4-triazine-3(2//)-thione (273), the open-chain compounds (274)- 276), thiosemicarbazide and sulfur (Scheme 49). Mechanisms for the formation of these products were suggested <84JHC905>... 

Some 1,2,4-triazines, such as l-(5,6-diphenyl-l,2,4-triazinyl-3)thiosemicarbazide 330 and 6-( 1-cyclohexenyl)-5(4//)-oxo-... 

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. 

With the colorless l,4-diphenyl-3-thiosemicarbazide (I), platinum forms a green complex of composition (Ci3HnN3S)2Pt which is only slightly soluble in water but readily soluble in chloroform. This reaction forms the basis of a spot test for platinum. 

Procedure. One drop of the test solution is mixed in a micro test tube with a few mg of solid l,4-diphenyl-3-thiosemicarbazide and then shaken with a little chloroform. A green color in the chloroform layer indicates the presence of platinum. 

---