3-Amino-5-mercapto-1,2,4-triazole

Klink KJ, Meade BJ. Dermal exposure to 3 amino 5 mercapto 1,2,4 triazole (AMT) induces sensitization and airway hyperactivity in BAFB/c mice. ToxicolSci2003 75(l) 89-98. 

IR data for Co(II), Ni(II) and Cu(II) complexes of pyridine-2-(17f)-thione-3-cyano-4,6-dimethyl-5-phenylazo) and related ligands show coordination through the thioenol S and cyano N atoms." " The Co(II), Ni(II), Zn(II) and Cd(II) complexes of lH-l,2,4-triazole-3-thiol and 3-amino-5-mercapto-1,2,4-triazole have IR spectra consistent with ligand coordination through the ring N and exocyclic S atoms." Rh, Ir, Pd and Pt complexes containing mono-, di- and trisubstituted thioureas, all show IR bands from -coordinated ligands." ... 

The use of an acidic solution of p-anisaldehyde in ethanol to detect aldehyde functionalities on polystyrene polymer supports has been reported (beads are treated with a freshly made solution of p-anisaldehyde (2.55 mL), ethanol (88 mL), sulfuric acid (9 mL), acetic acid (1 mL) and heated at 110°C for 4 min). The colour of the beads depends on the percentage of CHO content such that at 0% of CHO groups, the beads are colourless, -50% CHO content, the beads appear red and at 98% CHO the beads appear burgundy [Vdzquez and Albericio Tetrahedron Lett 42 6691 200]]. A different approach utilises 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (Purpald) as the visualizing agent for CHO groups. Resins containing aldehyde functionalities turn dark brown to purple after a 5 min reaction followed by a 10 minute air oxidation [Coumoyer et al. J Comb Chem 4 120 2002]. 

Triazole ring cleavage of the 7-amino-5-benzyl-5-mercapto-l,2,4-triazolo-[l,5-c]pyrimidinium iodide 135 at the N3-N4 bond occurred upon treatment with potassium carbonate to give the 4-amino-2-benzylmercapto-l-methyl-... 

Aldehydes 4-Amino-3-hydrazino-5-mercapto-1,2,4-triazole (Purpald reagent) Aldehydes yield violet chromatogram zones on a whitish-yellow background. Some alcohols form yellow to orange-colored chromatogram zones. [2]... 

Two 4-amino-3-mercaptol,2,4-triazole residues linked by a two-carbon bridge have been prepared by the reaction of thiocarbohydrazide with succinic acid 157a or malic acid 157b to give l,2-bis-(4-amino-5-mercapto-477-l,2,4-triazol-3-yl)ethan-l-ol 158a or l,2-bis-(4-amino-5-mercapto-477-l,2,4-triazol-3-yl)ethane 158b in yields of 56% and 60%, respectively (Equation 49) <2006PS(181)2361>. 

Several ring-closure reactions for [l,2,4]triazolo[3,4- ][l,3,4]thiadizines have been described, and all these procedures started from 3-mercapto-4-amino[l,2,4]triazole 135 (Scheme 26). A common structural feature of the reagents is the presence of the CH2X (X = halogen atom) moiety which allows the alkylation at the sulfur atom followed by a ring-closure reaction via an elimination step. Some typical ring closures are shown in Scheme 26. 

The most widely used method for the ring closure to the title ring system is the reaction of a 3-mercapto-4-amino[l,2,4]triazole compound with an a-halo-oxo reagent. The particular realizations of these syntheses are summarized in Table 4. Comparison of the reference lists shows that reactions with phenacylhalogenides and analogues (entry 1) is by far the best method. Synthesis of altogether more than 150 derivatives are described in... 

Table 4 Synthesis of [1,2,4]triazolo[3,4-b]thiadiazines by reaction of 3-mercapto-4-amino[1,2,4]triazoles with a-halo-oxo reagent...

Ring closures of 3-mercapto-4-amino[l,2,4]triazole with benzoin or related compounds is also a well-established approach for the synthesis of the title compounds (with Table 5, entry 5, (tosyloxy)methyl 2-hetarylketones were used). These procedures are summarized in Table 5. 

Mercapto-4-amino[l,2,4]triazole can also be transformed to derivatives of the title ring system by 1,3-dioxo reagents. These transformations are summarized in Table 6. In most of these cases, 5,5-dimethylcyclohexane-l,3-dione was used, and, accordingly, this procedure can lead to some cyclohexenyl-fused derivatives. 

Transformations of 5-substituted 3-mercapto-4-amino[l,2,4]triazoles 143 with bromomalonitrile are shown in Scheme 27. These reactions were carried out in ethanolic potassium hydroxide to yield A -phthalazinemethylene 144a, <2003PS1987> substituted 1-naphthyl-1-ethyl 144b, <2002HAC199> and 2-naphthyloxymethyl derivatives 144c, 2001PS223>. 

Qualitative spot tests for aldehydes, in the presence of ketones, are generally only reliable for water-soluble compounds. This problem can be overcome by the use of 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (Purpald , Aldrich Chemical Company) in the presence of Aliquat (Scheme 5.27). Under aerial oxidation, the initially formed colourless cyclic adduct changes colour through red to purple. The colourless cyclic aminal can also be formed by ketones, but only the adducts derived from the aldehydes are oxidized to the purple bicyclic aromatic system [28]. Weakly electrophilic aldehydes, e.g., 4-methoxybenzaldehyde, reacts slowly, but will give the positive coloration upon gentle heating to ca. 70°C for one or two minutes. 

Coumarinyl-substituted thiazolo[3,2-h][l,2,4]triazoles have also been reported. They are available in one step by reaction of 5-aryl-3-mercapto[l,2, 4]triazoles with 3-bromoacetylcoumarin (ethanol, reflux, 8 h yield 44-65%) (81AP435) or in a two-step reaction from the corresponding S-alkylated intermediates with PPA [93MI2 94IJC(B)579]. 2-Aminothiazolo[3,2-h][l,2,4]triazoles are also available from 3-mercaptotriazoles. Treatment of 5-amino-3-mercaptotriazole with chloroacetone (DMF, K2CO3) and subsequent acid-catalyzed cyclization yields 146 [90JAP(K)02/142797]. 

V-Amino-3-mercapto-1,2,4-triazoles (240) add DMAD to give adducts 241 derived from initial attack by sulfur.168... 

Amino-5-hydrazino-3-mercapto-4H-s-triazale, or 4- Am i no- 5-h yd ra z i no-4H-1,2,4-tri azol e-3-fhione(Called in Beil 4-Amino-3-hydrazono-3-tbion-l,2,4-triazolidin) (Called 4-Amino-3-hydrazino-5-mercapto-1,2,4-triazole in Refs 3,4 5), H2N-HN C=N-N or H,N N C-NH-NH. 

---