3-Mercapto-l,2,4-triazines

Substituted aminotriazinones have proved to be important synthons in heterocyclic syntheses. 4-Amino-6-methyl-3-mercapto-[l,2,4]triazin-5-one 32 reacted with bromomalononitrile in the presence of sodium hydroxide to afford the... 

A series of 4//.8//-1,2-4-triazino[3,4-//]-l,3,4-thiadiazin-4-ones 17 <2001IJB475> has been reported and obtained by condensation of 4-amino-6-substituted-3-mercapto-l,2,4-triazin-5(4//)-ones 35 with various phenacyl bromides (Equation 2) <2001IJB475>. 

Most of the cyclizations of the five-membered ring relating this type of fused [l,2,4]triazines concern the synthesis of [l,3,4]thiadiazolo[2,3-c][l,2,4]triazines. These synthetic approaches are similar in respect to the starting compound, which is a substituted 4-amino-3-mercapto[l,2,4]triazine-5(477)one 218 in each case. The ring-closure reactions can be classified into four related categories according to the reagent used aldehyde, isothiocyanate, carbon disulfide, or an acid. 

Further, 1,2,4-triazinones, 1,2,4-triazine thiones, and their numerous derivatives are of interest for the synthesis of biologically active compounds. For instance, 4-amino-6-arylmethyl-3-mercapto-l,2,4-triazin-5(4//)-ones were condensed with suitably substituted 5-aryl-2-furfurals or 5-aryl-2-furoic acids to obtain biologically active derivatives 201 and 202 which exhibit antibacterial activities compared to furacin (Figure 11) <2003IJH85>. 

A series of 4-amino-6-arylfuranylmethyl-3-mercapto-l,2,4-triazin-5(4//)-ones 339 (R = 4-chloro, 4-nitro, 4-bromo, 2-nitro, 3-nitro, 2-chloro), obtained by refluxing pyruvic acids 340 in ethanol with thiocarbohydrazide, show a good level of antibacterial activity (Figure 23) <2003IJB2649>. 

Several 3-mercapto-l,2,4-trizines have been synthesized through the condensation of thiosemicarbazide with diketones under microwave irradiation in a solventless system <06PS87>. The synthesis and cyclocondensation reactions of 3-substituted-5-(2-aminobenzyl)-l//-[l,2,4]triazin-6-ones have been reported <06JHC613>. 

Thus, 5-aryl-3-hydrazino[l,2,4]triazine 200 was reacted with acid chlorides to yield 201 <2004AF42>, and reaction of 5,6-diphenyl-3-hydrazino[l,2,4]triazine 202 with carbon disulfide yielded a 3-mercapto product 203 <2000PJS214>. 

The reaction of 5-mercapto-6-amino-l,2,4-triazin-3-one 143 with a-haloketones gives the thiazino[2,3-r ]-l,2,4-triazines 144 shown in Equation (21), although the publication lacks further detail (yields, for example, are not given) and focuses upon the synthesis of other heterocyclic systems <2001PS205>. 

Many 1,2,4-triazines form complexes with metal ions and can be used for their determination. Thus, 3- and/or 5-(2-pyridyl)-substituted 1,2,4-triazines (e.g. 820) can be used for the determination of iron (II), cobalt(II), nickel(II), zinc(II) and copper(I) ions, thallium and palladium ions can be analyzed by 6-phenyl- (821a) and 5,6-diphenyl-l,2,4-triazine-3-thione (821b), while osmium can be determined by 3-thioxo-l,2,4-triazin-5-one (822), 3-thioxo-dihydro-l,2,4-triazin-5-one (823), 6-mercapto-l,2,4-triazine-3,5-dione (824a), 6-mercapto-5-thioxo-l,2,4-triazin-3-one (824b) and 3,5-dithioxo-l,2,4-triazine-6-carboxyl-ates (825) <78HC(33)189, p. 1004). 

The IR spectra of Co(ll,lll) and Cu(ii) complexes of hydrazones obtained by the reaction of 5,6-diphenyl-3-hydrazino-l,2,4-triazine with furfural <2002TML398> and 2-acetylpyridine <2004JCR105> have been studied to determine the coordination sites of these ligands. In addition, Mn(ii), Ni(ii), and Cu(ll) complexes of hydrazones derived from 4-amino-3-mercapto-6-methyl-l,2,4-triazin-5(4//)-one were elucidated by IR spectra <2000SRI979>. 

Amino-3-hydrazino-5-mercapto-l,2,4-triazine (Purpald ) 402 is a well-established reagent for qualitative and quantitative detection of aldehydes. In the presence of an aldehyde or ketone, Purpald is transformed into a fused tetrahydrotetrazine intermediate 403. However, only with aldehydes, further oxidation of 403 takes place to give a deeply purple colored [l,2,4]triazolo[4,3-. ][l,2,4,5]tetrazine-3-thiol 404 (Scheme 95) <2000ALD28>. 

Triazinothiadiazines 24 and 25 <2002IJH287> containing sydnone and coumarin systems have also been prepared from 4-amino-3-mercapto-6-substituted-l,2,4-triazin-5-ones 38 as shown in Scheme 5. 

A third, not too widely used, approach is transformation of an iV-aminotriazine compound, as shown in Scheme 56. The 3-mercapto-4-amino[l,2,4]triazine derivative 361 was treated with an active methylene ketone and NBS in ethanol to yield the cyclized product 362 in moderate to excellent yield <2001JHC711>. A similar synthetic strategy was also applied in another case <2003KGS1844>. 

Chiral 4-(l-arylpropyl)amino-3-mercapto-6-methyl-4//-l, 2,4-triazin-5-ones were... 

The reactions of CpTiCl3 with 4-amino-3-mercapto-6-methyl-5-oxo-l,2,4-triazine and its Schiff bases (derived from benzaldehyde, 2-chlorobenzaldehyde, anisaldehyde, salicylaldehyde, 2-hydroxynaphthaldehyde, and 2-hydroxyace-tophenone) have been studied in THF and CH2G12 in the absence and presence of amine in different molar ratios.997... 

Amino-5(6)-methylthio-l,2,4-triazine ergeben mit Kohlenstoffdisulfid bzw. Aryl-isothio-cyanaten 2-Mercapto- bzw. 2-Arylamino-140 26V. 

Additionally, acetone cyanohydrin is an appropriate C-C reagent for the [4+2] condensation with thiosemicarba-zide, resulting in 3-mercapto-6,6-dimethyl-l,2,4-triazin-5-one (Scheme 145) <2002CHE992>. 

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