2,2-Diphenyl-l,3,4-thiadiazoline

Diphenyl-l,3,4-thiadiazoline, 3640 Diseleniumdisulfur tetranitride, 4763 Disulfur dinitride, 4749... 

Synthesis from l,2-Dithiole 3-thiones. 5-Aryl-l,2-dithiole-3-thiones (118) react with a-chlorobenzylidenephenylhydrazine (119), with simultaneous dithiole-ring opening and formation of (A -l,3,4-thiadiazolin-2-ylidine)-thioacetophenones (120). The use of ethyl bromo(phenylhydrazono)-acetate similarly affords (5-ethoxycarbonyl-3-phenyl-A -l,3,4-thiadiazolin-2-ylidene)thioacetophenone, which is saponifiable to the corresponding 5-carboxylic acid. The reactions resemble Huisgen s synthesis of iV-(3,5-diphenyl-A -l, 3,4-thiadiazolin-2-ylidene)benzamide from (119). 

Freund and Wolf10 reported that 2,4-diphenyl-l,2,4-thiadiazolidine-3,5-dithione was formed by heating l,3-diphenyl-2-thiourea with thiophosgene in benzene whereas, a 1,3-thiazetidine was produced at lower temperatures in ether (see Section II). Ohande181 has reported that 3,5-diamino-l,2,4-thiadiazoles are formed by the reaction of thiopseudoureas with carbon disulfide in the presence of bromine. Use has also been made of thioureas in the synthesis of 1,3,4-thiadiazolines (79) via reaction with the halohydrazones 78.185,186 The analogous reaction with solenoureas was recently reported by Bulka and Ehlers187 to yield 1,3,4-selenadiazolines. 

Electrochemical reduction of various 3,4-disubstituted-l,2,5-thiadiazole 1,1-dioxides (3,4-diphenyl- 10, phenanthro[9,10]- 51, and acenaphtho[l,2]- 53) gave the corresponding thiadiazoline 1,1-dioxides <1999CJC511>. Voltammetric and bulk electrolysis electroreduction of 3,4-diphenyl-l,2,5-thiadiazole 1-oxide 9 at ca. —1.5 V, in acetonitrile, gave 3,4-diphenyl-l,2,5-thiadiazole 8 (50%) and 2,4,6-triphenyl-l,3,5-triazine 54 (30%) (Equation 3) <2000TL3531>. 

The complexes ZnX [X = Q, Br or I L = [3,5-diphenyl-A4-(l,3,4-thiadiazoline)-2-ylidene]-p-methoxythioacetophenone or -p-methoxyacetophenone] have been isolated.856 On the basis of IR evidence the metal is believed to be trigonal bipyramidally coordinated with the ligand acting in a bidentate manner. The complexes are thus best formulated as [Znl XjX. 

The 3-phenyl (m.p. 162° C) and the 3-/)-tolyl (m.p. l66° C) derivative of (XCVII) have been described. The reaction of carbon disulfide with 3,5-diphenyl-5-amino-/l3-l,2.4-oxadiazoline (XCVIII) also yields 3-phenyl-J2-l,2,4-thiadiazoline-5-thione (332). This is in fact the same reaction since (XCVIII) partially decomposes into benzonitrile and benzamidoxime. 

The interaction of thiobenzoyl isocyanates (318) and IV.lV -diphenyl sulfur diimide yields 2,5-diaryl-A4-l,2,4-thiadiazolin-3-ones (320) as very minor by-products (2%), presumably by way of the intermediate adducts (319).238... 

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