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1.2.4- Triazole 2- amino-5- -, ring

When metronidazole (89) and other 4(5)-nitroimidazoles are treated with hydrazine the products include 4-amino-4//-1,2,4-triazole and ring-opened species. The 4-nitro isomers are less reactive than the 5-nitro compounds (which are also known to be more biologically active). A proposed rationale for the reactions (Equation (28)) involves initial nucleophilic addition of hydrazine at C-... [Pg.131]

Several interesting 1,2,4-triazole fused-ring systems have been reported. Reaction of aryl nitriles with 4-amino-l,2,4-triazine-3-thiones in the presence of potassium fcrf-butoxide afforded... [Pg.239]

Ring substituents can have a considerable effect on the acidity of the system. In the 1,2,4-triazole series a 3-amino group decreases the acidity to 11.1, a 3-methyl group to 10.7, whereas a 3-phenyl group Increases the acidity to 9.6, and 3,5-dlchloro substitution to 5.2 (71PMH(3)1). [Pg.51]

Amination at an azole ring nitrogen is known for Af-unsubstituted azoles. Thus 4,5-diphenyl-1,2,3-triazole with hydroxylamine-O-sulfonic acid gives approximately equal amounts of the 1- (104) and 2-amino derivatives (105) (74AHC(16)33). Pyrazole affords (106) and indazole gives comparable amounts of the 1- and 2-amino derivatives. [Pg.55]

Other amino substituted isoxazoles undergo ring-opening reactions on treatment with base. Thus the amidine derivative (249) gave the triazole (250) (64TL149), while the triazene (251) on reaction with ammonia gave the tetrazole (252) (64X461). [Pg.55]

Pyrazolino[2,3-c][l,2,3]triazoles, 5, 702 Pyrazolium hydroxide, l,2-dimethyl-3,5-diphenylanhydro-4-hydroxy-IR spectra, 5, 201 Pyrazolium salts dequatemization, 5, 269 H NMR, 5, 185 hydrogen exchange at ring carbon, 5, 245 mesoionic compounds, 5, 171 nitrodebromination, 5, 237 reactivity, 5, 217 reduction, 5, 68, 243 synthesis, 5, 156 UV spectra, 5, 199 Pyrazolium salts, amino-reactions, 5, 262 Pyrazolium salts, bromo-nucleophilic displacements, 5, 266 Pyrazolium salts, 1,2-dimethyl-deuteration, 5, 175, 245 hydrogen exchange, 5, 71 acid-catalyzed, 5, 239 reactions... [Pg.777]

A combination of the preceding type of synthesis and of cyclization of 4-amino-5-arylazopyrimidine can be seen in the novel procedure of Richter and Taylor. Proceeding from phenylazomalonamide-amidine hydrochloride (180), they actually close both rings in this synthesis. The pyrimidine ring (183) is closed by formamide, the triazole (181) one by oxidative cyclization in the presence of cupric sulfate. Both possible sequences of cyclization were used. The synthetic possibilities of this procedure follow from the combination of the two parts. The synthesis was used for 7-substituted 2-phenyl-l,2,3-triazolo[4,5-d]-pyrimidines (184, 185). An analogous procedure was employed to prepare the 7-amino derivatives (188) from phenylazomalondiamidine (186). [Pg.246]

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-... [Pg.369]

Other examples of nucleophilic attack on a furoxan ring leading to ring opening/recyclization are the formation of 1,2,3-triazole 1-oxides 198 from 4-alkylamino-3-nitrofuroxans 197 and alkylamines (Scheme 129). 3-Amino-4-nitrofurazan was observed as by-product (95MC194, 96CHE580, 96KGS675). [Pg.128]

The diazotization of heteroaromatic amines is basically analogous to that of aromatic amines. Among the five-membered systems the amino-azoles (pyrroles, diazoles, triazoles, tetrazoles, oxazoles, isooxazoles, thia-, selena-, and dithiazoles) have all been diazotized. In general, diazotization in dilute mineral acid is possible, but diazotization in concentrated sulfuric acid (nitrosylsulfuric acid, see Sec. 2.2) or in organic solvents using an ester of nitrous acid (ethyl or isopentyl nitrite) is often preferable. Amino derivatives of aromatic heterocycles without ring nitrogen (furan and thiophene) can also be diazotized. [Pg.16]

More recently, Stepanov et al. (1989) investigated the acid-base properties of the zwitterion 3.22 which is obtained in the diazotization of 5-amino-3-nitro-l,2,4-triazole. Under alkaline conditions the (Z)-diazoate dianion 3.23 is formed. It can be isomerized thermally to give the (E)-diazoate dianion 3.24. If the solution of this compound is acidified, the primary addition of a proton takes place at the anionic ring nitrogen yielding 3.25, and subsequently the hydrogen-bond-stabilized (Z)-iso-mer (3.26). Further acidification gives the nitrosoamine (3.27). [Pg.61]

As shown by Heindel and Corley (1979), ring closure also takes place if the nucleophilic nitrogen is part of a heterocycle, as in the diazotization of 5-amino-3-methyl-2-H-l,2,4-benzothiadiazine-l, 1-dioxide (6.50). In the tricyclic compound 6.51 formed initially, the thiadiazinedioxide ring is opened rapidly in water, forming 1-acetyl-7-aminosulfonyl-l-i/-benzo-l,2,3-triazole (6.52). [Pg.133]

Diacetylcyclopropane reacts with 3-amino-l, 2,4-triazole in acetic acid (either aqueous or glacial) to give triazolopyrimidines 28 <%1ZV1322>, whilst a selection of fiised-ring pyrimidines, for example the l,2,3-triazolo[4,S-prepared using amino hetmoarenecarboxamides and esters <96H(42)691 >. [Pg.272]

Ligands with S donors in addition to N and or O donors bound to Co11 are reasonably large in number. For example, the 4-amino-3-alkyl-l,2,4-triazole-5-thione can bind Co11 as a chelate employing the primary amine and thione substituents on the five-membered ring,510 whereas the trifluoromethyl ligand (afmt) forms [Co(afmt)2(H20)2](N03)2, defined as the A -irons isomer... [Pg.53]

Amino 4-oxo 4//-pyrimido[l,2-4]pyridazin-3-diazonium tetrafluoroborates 73 underwent ring transformation into l-(pyridazin-3-yl)-l//-l,2,3-triazole-4-carboxylates 74 on heating in dry MeOH. Yields dropped drastically when EtOH, instead of MeOH, was used as solvent (Equation 6) <2002ARK143>. [Pg.270]

Base-mediated intramolecular cyclization of an amino-substituted triazole onto the chloropyrazole of compound 257 with loss of HG1 generates the central pyrimidine ring of 258 (Equation 70) <2004JCM50, 2004SC151>. [Pg.740]

In an example given in Scheme 51, tricyclic system 331 is generated by cyclocondensation between the ethoxycarbonyl group at C-5 of the triazole ring and the amino group of the substituent at N-l. The process that starts from catalytic reduction of the nitro group in derivative 329 does not stop at amine 330, but the subsequent spontaneous cyclocondensation leads directly to product 331 that is isolated in 60% yield <2002EJM565>. [Pg.43]

Ethyl 3-azido-l-methyl-177-indole-2-carboxylate 361 is prepared in 70% yield by diazotization of amine 360 followed by substitution of the created diazonium group with sodium azide. In cycloadditions with nitrile anions, azide 361 forms triazole intermediates 362. However, under the reaction conditions, cyclocondensation of the amino and ethoxycarbonyl groups in 362 results in formation of an additional ring. This domino process provides efficiently 4/7-indolo[2,3-i ]l,2,3-triazolo[l,5- ]pyrimidines 363 in 70-80% yield (Scheme 57) <2006TL2187>. [Pg.46]


See other pages where 1.2.4- Triazole 2- amino-5- -, ring is mentioned: [Pg.78]    [Pg.210]    [Pg.742]    [Pg.742]    [Pg.259]    [Pg.109]    [Pg.128]    [Pg.134]    [Pg.88]    [Pg.243]    [Pg.43]    [Pg.130]    [Pg.136]    [Pg.125]    [Pg.873]    [Pg.160]    [Pg.10]    [Pg.272]    [Pg.123]    [Pg.930]    [Pg.298]    [Pg.317]    [Pg.903]    [Pg.386]    [Pg.4]    [Pg.46]   


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Triazole ring

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