Amines 1,2,4-triazoles

Similarly, thiazol-2-amine, 5-ethyl-l,3,4-thiadiazol-2-amine, 5-methylisoxazol-3-amine. 1,2,4-triazol-3-amine and benzimidazol-2-amine give the corresponding heterocyclic systems on reaction with 2-aza-l-chloro-l,3-bis(dimethylamino)-3-phenylpropenylium perchlorate.490... 

The reaction of 2-amino-4-methyl-l,l,l-trifluoromethyl-2-butene-4-one with thiosemicarbazide forms 5-hydroxy-5-trifluoromethyl-2-pyrazoline, and with derivatives 3-amine-1,2,4-triazoles forms derivatives triazolo[l,5-a]pyrimidine (02IZV332) (Scheme 75). 

The most common corrosion inhibitors, which may form protective films on the metal surfaces, are borates, molybdates, nitrates, nitrites, phosphates, silicates, amines, triazoles, and thiazioles (e.g., monoethanolamine, urotropin, thiodiglycol, and mercaptobenzothiazole). The addition of such inhibitors does not effectively protect against corrosion [137]. Some corrosion inhibitors are shown in Figure 14-3. 

ROfePX (BnO)aPNEt, (ElOfePa amine triazole, (Pr2NEt... 

The Pfizer anti-fungal compound fluconazole 60 is a more advanced example of such disconnections.5 It has two identical 1,2-diX relationships between nitrogen and the OH group. You might think that we can make both the same way, but not so. The first disconnection is easy we want the aromatic amine triazole 62 to combine with the epoxide 61 at its less substituted end. 

Fig. 12.49. Action of corrosion inhibitors, (a) Anodic inhibitors. Examples Chromate, nitrite, molybdate, tungstate, orthophosphate, silicate, benzoate, (b) Cathodic inhibitors. Examples Ca(HC03)2, ZnS04, Cr2(S04)3, NiS04 phosphate, aminoethylene phosphate (AMP), Ag3+, Sb3+ (on iron) Hg (on zinc), (c) Mixed inhibitors. Examples organic inhibitors containing nitrogen and/or sulfur (e.g., amines, triazoles, thiazoles, alkylthioureas) inorganic inhibitors (e.g., arsenite, arsenate, selenate). (Reprinted from G. Ranglen, Corrosion of Metals, p. 165,1985 with permission from Chapman Hall.)...

Additives are used to coat the metal surfaces and prevent O2 and acids from reacting and to prevent foaming. These include borates, molybdates, nitrates, nitrites, phosphates, silicates, amines, triazoles, and thiazoles. Acids are formed by Cl, 804 and the oxidation products of ethylene glycol at high temperatures. Foaming is caused by entrapped air and is retarded by silicones, polyglycols, or oil. Most of the air comes from an improperly filled overflow container. 

Organometallic compounds of Al, Cu, Zn, but mainly of Ni in the form of salts of organic acids, alcoholates, phenolates, amines, triazols. 

Figure 9-4. Action of inhibitor (- without, — with), a) mixed (e.g., amine, triazole), b) cathodic (zinc salts), c) anodic (nitrite, molybdate). cor is the corrosion potential, cor,inh the corrosion potential with inhibitor, o the equilibrium potential of the anodic reaction, and Eq, . the equilibrium potential of the cathodic reaction.

Fig. 1. HeterocycHc amines usedia azo dyes, (a) 2-Amino-6-nitrohenzothiazo1e [6285-57-0], (b) 3-amiao-5-nitro-2,l-benzisothiazole [14346-19-1], (c) 3-amiQo-4JT-l,2,4-triazole [65312-61 -0], (d) 5-amiQo-l,2,4-thiadiazole [7552-07-0, (e) 4,4 -diamiQo-2,2 -biphenylsulfone [6259-19-4], (f)...

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. 

Halogeno-l-methyl-l,2,3-triazoles undergo substitution reactions with amines, but the 4-halogeno analogs do not. 5-Chloro-l,4-diphenyl-l,2,3-triazole with sodium cyanide in DMSO gives the cyano derivative (63JCS2032). 1-Substituted 3-chloro- and 5-chloro-l,2,4-triazoles both react with amines. 

Diacylhydrazines (32) on heating with a primary amine undergo cyclization to the 1,2,4-triazole derivative (38). It is assumed that the amidrazone (37) is an intermediate in the reaction. Most practical syntheses of 1,2,4-triazoles now utilize an amidrazone or a derivative of this alicyclic intermediate containing three nitrogen atoms, and these variations are discussed in Chapter 4.12. 

That aminals and enamines are in equilibrium under certain conditions has been demonstrated (38). l,l-Di(N-morpholino)ethane 18, when heated with excess diethylamine for 24 hr at 60 and then treated with 4-nitro-phenylazide, gave the triazole (19) in 80% yield. The authors contend that... 

An indole protected by a Mannich reaction with formaldehyde and dimethyl-amine is stable to lithiation. The protective group is removed with NaBH4 (EtOH, THE, reflux). The related piperidine analogue has been used similarly for the protection of a triazole. ... 

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. 

Hydroxyenones have also been used in catalytic amide formation, although 1,2,4-triazole is required as a co-catalyst. Assumed protonation of the Breslow intermediate and tautomerisation generates an acylazolium intermediate, which is trapped by triazole, releasing the NHC and generating the acyltriazole 60 that is the active acylating agent for the amine (Scheme 12.11) [16]. 

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