5- Amino-3-methyl-1,2,4-thiadiazole

Blajiev, O. and A. Hubin, Inhibition of copper corrosion in chloride solutions by amino-mercapto-thiadiazol and methyl-mercapto-thiadiazol An impedance spectroscopy and a quantum-chemical investigation. Electrochimica Acta, 2004. 49(17-18) p. 2761-2770. 

Value for 5-acetyl-3-methylsydnonimine (800MR(I3)274>. Value for 2-amino-5-methyl-l,3,4-thiadiazole 78H(ii)i2i>. 

Amino-l,2,5-thiadiazole is chlorinated or brominated at the 4-position at 20°C in acetic acid. 3-Methyl-l,2,5-thiadiazole can also be chlorinated in the 4-position (68AHC(9)107). Bromination of 2-amino-l,3,4-thiadiazole succeeds in the 5-position (65ACS2434). 

Pyrazblin-5-one, 3-alkyl-(l,2,4-thiadiazol-5-yl)-reactions, 6, 483 2-Pyrazolin-5-one, 3-amino-tautomerism, 5, 215 2-Pyrazolin-5-one, 4,4-diazido-rearrangement, 5, 720 2-Pyrazolin-5-one, 3-hydroxy-tautomerism, 5, 215 2-Pyrazolin-5-one, 3-methyl-1 -phenyl-reactions, 5, 252... 

Thiadiazole, 2-amino-5-methyl-melting point, 6, 555 sulfonamide derivatives... 

The structure of only one 1,2,4-thiadiazole salt has been determined. Unambiguous synthesis of the imino compound obtained on alkali treatment of the salt formed by the reactions of methyl iodide with 5-amino-1,2,4-thiadiazole established that the salt possesses structure 7 136 pjjjg quatemization exactly parallels the reaction occurring in... 

Ethyl iodide and 5-amino-2-methyl-l,3,4-thiadiazole react at 110° to give the N-3 salt (78 R = Me, R = NH2, R" = Et), as shown by the presence of the very reactive methyl group this salt is also used to prepare cyanine dyes. The slow quatemization at the ring-nitrogen atom furthest from the amino group is consistent with the reactions observed in other ring systems. As would be e pected, 5-alkylthio-2-methyl-l,3,4-thiadiazoles form salts at the N-3 (78 R = Me, R - S-alkyl).i ... 

Chemical Name (6R-trans)-3-([(5-methyl-1,3,4-thiadiazol-2-yl)thio] methyl)-8-oxo-7-([(1-H-tetrazol-1 -yl)acetyl] amino)-5-thia-1-azabicyclo[4.2.0] oct-2-ene-2-carboxylic acid sodium salt... 

Chemical Name 4-amino-N-(5-methyl-1,3,4-thiadiazol-2-yl)benzenesulfonamide Common Name Sulfamethylthiadiazole Structural Formula A ... 

Mg (3-methacryloxy)propyl, methyl, phenyl, 3-aminopropyl, 3-mercaptopropyl, [n-(2-aminoethyl)-3-aminopropyl], [(10-amino)-4,7-diazanonyl], hexadecyl, n-propyl-ethylenediamine, n-propyltriethylenediamine, 3-chloropropyl, 5 -amino-1,3,4-thiadiazol-2-thiol, (CH3CH20)Si(CH2)3NHC(0)NH-R (R = 3-propyl, 3-pentyl, 3-heptyl) [11-13,15,16,18,19,21-23,26,33]... 

The thermal decomposition of some 3,5-disubstituted-l,2,4-thiadiazoles has been studied and some nonisothermal kinetic parameters have been reported <1986MI239>. Polarographic measurements of a series of methylated 5-amino-l,2,4-thiadiazoles show that thiadiazoles are not reducible in methanolic lithium chloride solution, while thiadiazolines are uniformily reduced at 0.5 = — 1.6 0.02 V. This technique has been used to assign structures to compounds which may exist theoretically as either thiadiazoles or thiadiazolines <1984CHEC(6)463>. The photoelectron spectrum for 1,2,4-thiadiazole has been published <1996CHEC-II(4)307>. 

Thiadiazoles are weak bases. They form salts with mineral acids and addition compounds with heavy-metal salts. Methylation of 5-amino-l,2,4-thiadiazoles 17 leads to the product of methylation at the 4-position 18 (Equation 2) <1996CHEC-II(4)307>. More recently, the reaction of the 3-methylthio derivative 19 with methyl iodide led to methylation at N-4 to afford product 20 (Equation 3) <2001CHE1005>. 

Amino-5-methyl-l,3,4-thiadiazole 48 reacts with chloroacetone to give the N-alkylated thiadiazolimine 49 (Equation 4) <2000AF550> and iV-alkylation of the 2,5-diphenyl- and 2,5-dimethyl-l,3,4-thiadiazole 50a and 50b with trimethylsilylmethyl trifluoromethanesulfonate gave the corresponding 1,3,4-thiadiazolium salts 51 (Equation 5) <2002J(P 1)2851 >. A comprehensive study of the quarternization of the 2,5-disubstituted thiadiazoles has been covered in CHEC(1984) <1984CHEC(6)545>. 

Substituents on the ring nitrogen can often cyclize to afford fused 1,3,4-thiadiazoles (see also Volume 9). The N-substituent on the l-(2-amino-5-methyl-3-[l,3,4]thiadiazolyl)acetone 49 was annulated on the ring when treated with HBr (Equation 38) <2000AF550>. 

The reaction of commercially available 2-amino-5-methyl-l,3,4-thiadiazole 451 (R Me) with chloroacetone followed by treatment with 1M HBr provides 2,6-dimethylimidazo[2,l- ][l,3,4]thiadiazole 161 (Equation 103) (Table 59) <2000AF550>. 

The Schiff base derivatives 73 of the 3-hetaryl-substituted 4-amino-3-thiol-l,2,4-triazoles, on treatment with acetic anhydride, undergo cyclization to give the corresponding 3-substituted-5-acetyl-5,6-dihydro-6-phenyl[l,2,4]triazolo[3,4-7][l,3,4]thiadiazoles 76 (Equation 16) <1990IJB135>. Similar treatment of 4-(A-bcnzoylamino)-4,5-dihydro-l-methyl-3-mcthylthio-1 //-[ 1,2,4 triazolc-5-thione 77 leads to the [l,2,4]triazolo[3,4-4][l,3,4]thiadiazolium trifluoromethanesulfonate 78 (Equation 17) <1986LA1540>. 

Contrasting with the reported formation of fused [l,3,4]thiadiazole rings in the course of the reaction of 3-substituted-4-amino-5-thio-47/-[l,2,4]triazoles 83 with various isothiocyanates (cf. Section 11.07.8.3, Table 3), the reactions with methyl isothiocyanate and with phenylisocyanate afford 3,7-disubstituted-6,7-dihydro-57/-[l,2,4]triazolo[4,3-f] [l,2,4]triazole-6-thiones 110 and -triazole-6-ones 111, respectively (Equation 29) <1986MI607, 1992IJB167>.The same reaction of 4-amino-l-methyl-3,5-bis(methylthio)[l,2,4]triazolium iodide 112 with aryl isothiocyanates yields the mesoionic compounds 113 (Equation 30) <1984TL5427, 1986T2121>. 

In the presence of triethylamine, the reaction of 2-amino-5-methyl[l,3,4]thiadiazole 134 with 2-benzyl-5-chloro-[l,2,4]thiadiazol-2-one 135 gives 3-(benzylcarbamoylimino)-6-methyl-3//-[l,3,4]thiadiazolo[2,3-c][l,2,4]thiadiazole 138. Presumably, the first-formed intermediate 136 rearranges through the thiapentalene intermediate 137 to the fused thiadiazole product 138 (Scheme 10) <1994T7019>. 

Two other results should be reviewed here, too. The substituted thiadiazolo[3,2-trifluoromethyl groups) was described by Sokolov and Aksinenko <2003IZV2053> 2-amino-5-methyl[l,3,4]thiadiazole 165 was heated with iV-ethoxycarbonyl-bis-trifluoroacetone imine in DMF in the presence of />-toluenesulfonic acid to yield the cyclized product 166 in good yield (77%). 

The reactions of 2-amino-1,3,4-thiadiazoles and diethyl 1-ethoxyethyli-denemalonate in diglyme at 140°C for 20 hr gave 7-methyl-1,3,4-thiadia-zolo[3,2-a]pyrimidine-6-carboxylates (672) in 14-25% yields after column chromatography (86FES737). Reactions in ethanol or dimethylacetamide were unsuccessful. 

Amino-3-methyl-l,2,4-thiadiazole was reacted with EMME in boiling trichlorobenzene to give 1,2,4-thiadiazolo[4,5-a]pyrimidine-6-carboxylate (1132) (59JOC779). 

The cyclocondensation of 2-amino-5-(4-morpholinyl)l,3,4-thiadiazole and diethyl 1-ethoxyethylidenemalonate at 150°C for 20 min gave 7-methyl-... 

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