Phenyl benzaldehyde thiosemicarbazone

Amino-5-phenyl-l,3,4-thiadiazole is reduced by sodium amalgam to benzaldehyde thiosemicarbazone, but the 5-H and 5-methyl analogs do not react (68AHC(9)165, p. 197) (see also Scheme 9 for LAH reduction). 

Phenyl Bis[henzaldehyde thiosemicaihazone] Tellurium Chloride2 A solution of 1.0 g (3.2 mmol) phenyl tellurium trichloride in 30 ml methanol is added to a solution of 2.3 g (12.8 mmol) benzaldehyde thiosemicarbazone in 30 ml of warm water. The mixture is stirred for 0.5 h and then set aside for 12 h. The yellow crystals of the product arc filtered and recrystallized from methanol yield 79% m.p. 70- 72°. 

Sodium amalgam reduced 2-amino-5-phenyl-1,3,4-thiadiazole (38) to benzaldehyde thiosemicarbazone, whereas the 5-H and 5-methyl analogs were unaffected. The latter compounds could not be reduced polarographically, whereas 38 gave a half wave potential of —1.940 volts. 

Irradiation of 2-methyl-4-phenyl-substituted benzaldehyde thiosemicarbazones (171) leads to the corresponding A -l,2,4-triazohne-5-thione derivatives (173) through the formation of stable 1,2,4-tria-zoHdine-5-thione derivatives (172) (Scheme 27). Irradiation of N-acylthiourea (174) in the presence of triethylamine gives thiourea (175) and benzothiazoles (176) via an electron-transfer mechanism. A photochemicaUy induced Dimroth rearrangement has been reported in the l,2-thiazolino[5.4-d]-l,2-thiazoline-3,6-dithione (177) and yields the 3ff,6ff-l,2-dithiolo[4.3-c]-l,2-dithiole (178). ... 

Disubstituted 4-phenyl-5-phenylimino-l,3,4-thiadiazolines (203 X = NPh) are prepared by the reaction of phenyl isothiocyanate with ketonic phenylhydrazones in DMF in the presence of sodium hydride. Replacing the isothiocyanate with carbon disulfide leads to (203 X = S). Aliphatic aldehydes react similarly however, benzaldehyde phenyl-hydrazone furnishes the thiosemicarbazone which on thermolysis yields the thiadiazoline (204). The structures of these compounds are supported by detailed spectroscopic measurements (80JCS(P1)574>. 

When the thiosemicarbazones of benzaldehyde, 2-hydroxybenzaldehyde, methyl phenyl ketone, or methyl 2-hydroxyphenyl ketone were reacted with aryl tellurium trichlorides, reduction to the aryl tellurium chlorides occurred. The aryl tellurium chlorides were stabilized by coordination to excess thiosemicarbazone2. 

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