Dithiocarbazic - from

The synthesis of a series of thiazolo[2,3-c][l,2,4]triazole derivative 33 has been approached by base-mediated intramolecular cyclization of bromide 349 or acid-promoted ring closure of alcohol 350, obtained from pyrazinoyl-dithiocarbazate 348 (Scheme 33) <2004PS(179)2519>. 

Table 98 Complexes with Schift Bases Derived from Py ridine-2-carbaldehyde, Thiosemicarbazide, Dithiocarbazic Add and with Hydrazones... 

The nickel(II) complexes with thiosemicarhazides acting as neutral ligands, HL, are numerous and have been reviewed elsewhere.2415 Selected examples of square planar and six-coordinate complexes are given in Table 100. Some examples of complexes prepared with tridentate Schiff bases derived from either thiosemicarbazide or dithiocarbazic acid are given in Tables 97 and 98, and examples of complexes with bidentate Schiff bases are reported in Table 100. 

The main route to A2-oxadiazoline-5-thiones (83 R1 = alkyl, aryl, C02Et, R2 = H) is the cyclization of dithiocarbazates (88) prepared from acylhydrazines (89 R2 = H) and carbon disulfide. The ester (83 R1 = C02Et, R2 = H), obtained by this method, has been hydrolyzed... 

Schiff-base ligands coordinated to Ti via chelated S, N, and O-atoms are proposed in several systems including those derived from dithiocarbazates,895-897 benzothiazoline, and 2-(salicyl-ideneamino)benzenethiol.899... 

The hydrazones of thiocarbohydrazides also react in this manner (304). The 5-amino-.d4-1,3,4-thiadiazoline-2-thiones, which may be prepared from thiosemicarbazides and carbon disulfide, are listed in Table 19-The preparation of these compounds from dithiocarbazic acid esters and isothiocyanates in basic medium is discussed in Section VII.7. It must be pointed out that the numbering of the substituents in Guha s paper (146) is not always very clear so that, for the last three substances in Table 19, there is some doubt about the position of the substituents. 

The hydrazone structure was preferred because of the ease with which S,S -dialkylation of N-aryl dithiocarbazates is known to take place and because acid hydrolysis of the product yields 1,3-dithio]sn-2-cne (CCXXIV) and the aryl hydrazine. The hydrazone (CCXXIII, R2=1 3=R.i=1 5 =H, Ri=CfiH5), independently prepared from 2-imino-1,3-dithiolane (CCX X. V ) 374 and phenylhydrazine 254), has the same melting point (94° C) and causes no lowering of the melting point when mixed with the product prepared from N-phenyl dithiocarbazate and 1,2-dibromoethane (m.p. 

These same y)-2-thio-T3,4-thiadiazolines (CCXXVIII) may also be obtained from the reaction of carboxylic acid chlorides with dithiocarbazates 17, 18, 19, 28, 62, 67 (scheme 2e, method B, Table 39)-... 

Dithiocarbazates (CCXV) and phosgene react to give i,3>4-thia-diazolidin-5-one-2-thiones (CCXXXIII). An example of this is the formation of 4-phenyl-t,3,4-thiadiazolidin-5-one-2-thione (m.p. 86—7° C) from N-phenyldithiocarbazic acid and phosgene 57). 

This preparation is illustrated by the formation of (CCXXXIX, Ri=R2=CH3, R3=C6H5) with m.p. 185° C and of (CCXXXIX, Ri = Rg=C2H5, R3=CgH5) with m.p. 211° C from S-ethyl dithiocarbazate with N,N-dimethyl-N -phenyl-S-methylthiourea and N,N-diethyI-N -phenyl-S-methylthiourea respectively. 

Na (2.3 g, 0.1 mol) was dissolved in EtOH (50 mL) and the the solution was cooled and treated with methyl dithiocarbazate (12.6 g, 0.1 mol). With ice cooling over 2 h, phenacyl chloride (15.5 g, 0.1 mol) in EtOH (100 mL) was added dropwise to the green solution. The mixture changed color to brown, then red-brown and a crystalline precipitate separated. After 12 h this was filtered under suction and the residue washed with copious H20 lo remove NaCl yield 18 g (81 %) nip 115°C pale-yellow platelets (from EtOH). 

Similarly, 6//(or 4//)-l,3,4-thiadiazine-2(3//)-thiones 13a-e and 14a, bean be prepared from the dimeric chloronitroso compounds 10 and the dithiocarbazic acid derivatives 11. The [3-ox-iminoalkyl dithiocarbazatcs 12 formed as intermediates can also be isolated.54... 

Dihydro-5-phenyl-2//-l,3,4-thiadiazine-2-thione (215) is obtained as a by-product (29%) from the cyclization of the phenacyl dithiocarbazate (214) under strong acid conditions (Scheme 28). The major product, 3-amino-4-phenylthiazoline-2(3//)-thione (216 48%), becomes the sole product if the reaction time (0.5 h) is extended <85H(23)3099>. 

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