Triazoles sodium azide

Nitric acid may be precipitated by nitron [2218-94-2] (4,5-dihydro-l,4-diphenyl-3,5-phenylimino-l,2,4-triazole). The yellow precipitate maybe seen at dilutions as low as 1 60,000 at 25°C or 1 80,000 at 0°C. To prevent nitrous acid from interfering with the test results, it may be removed by treating the solution with hydrazine sulfate, sodium azide, or sulfamic acid. 

According to Hofman-Bang carbon sulfide selenide, CSSe, catalyzes the iodine-azide reaction but is at the same time decomposed with the formation of selenium. Experiments, in both this laboratory and that of Hofman-Bang have shown that carbon diselenide reacts with sodium azide (in aqueous or aqueous-alcoholic solution) with immediate precipitation of red selenium even at — 20° C. //a selena-triazole is formed in this reaction it must be extremely unstable. 

Intramolecular dipolar azide-olefin cycloaddition of 723 took place upon heating in benzene to afford 724 (83JA3273). An alternative rearrangement process can take place upon photolysis of 724 to give 725. Mesylation of 4-(3-hydroxypropyl)-2,4,6-trimethyl-2,5-cyclohexadiene-l-one (78JA4618) and subsequent treatment with sodium azide in DMF afforded the respective azide 726 which underwent intramolecular cycloaddition to afford the triazoline 727 (83JOC2432). Irradiation of 727 gave the triazole derivative 728 (Scheme 126). 

A microwave-assisted three-component reaction has been used to prepare a series of 1,4-disubstituted-1,2,3-triazoles with complete control of regiose-lectivity by click chemistry , a fast and efficient approach to novel functionalized compounds using near perfect reactions [76]. In this user-friendly procedure for the copper(l) catalyzed 1,3-dipolar cycloaddition of azides and alkynes, irradiation of an alkyl halide, sodium azide, an alkyne and the Cu(l) catalyst, produced by the comproportionation of Cu(0) and Cu(ll), at 125 °C for 10-15 min, or at 75 °C for certain substrates, generated the organic azide in situ and gave the 1,4-disubstituted regioisomer 43 in 81-93% yield, with no contamination by the 1,5-regioisomer (Scheme 18). 

Another important click reaction is the cycloaddition of azides. The addition of sodium azide to nitriles to give l//-tetrazoles is shown to proceed readily in water with zinc salts as catalysts (Eq. 11.71).122 The scope of the reaction is quite broad a variety of aromatic nitriles, activated and nonactivated alkyl nitriles, substituted vinyl nitriles, thiocyanates, and cyanamides have all been shown to be viable substrates for this reaction. The reaction of an arylacetylene with an azide in hot water gave 1,4-disubstituted 1,2,3-triazoles in high yields,123 while a similar reaction between a terminal aliphatic alkyne and an azide (except 111 - nitroazidobenzcnc) afforded a mixture of regioisomers with... 

Pyranopyridines. The chlorobenzopyranoquinolone 325 reacts with hydrazides to give a triazole-fused ring system, such as in compound 326. Likewise, reaction with sodium azide gives the tetrazolo-fused product 327 (Scheme 79) <2003IJB2567>. 

A three-component coupling was used to prepare a series of 1,4-disubstituted-l,2,3-triazoles 129 from the corresponding acetylated Baylis-Hillman adducts 127, sodium azide and terminal alkynes 128 <06TL3059>. This same reaction was also carried out in either water or in... 

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>. 

Azide 367 is prepared from 4-r -butyl-2-nitroaniline in 76% yield by its diazotization followed by treatment with sodium azide. In a 1,3-dipolar cycloaddition with cyanoacetamide, azide 367 is converted to triazole 368 that without separation is directly subjected to Dimroth rearrangement to give derivative 369 in 46% yield. Reduction of the nitro group provides ortfc-phenylenediamine 371 in 91% yield <2000EJM715>. Cyclocondensation of diamine 371 with phosgene furnishes benzimidazol-2-one 370 in 39% yield, whereas its reaction with sodium nitrite in 18% HC1 leads to benzotriazole derivative 372, which is isolated in 66% yield (Scheme 59). Products 370 and 372 exhibit potassium channel activating ability <2001FA841>. 

An example of asymmetric synthesis involving cycloaddition of an azide to dimethyl acetylenedicarboxylate is depicted in Scheme 172. Thus, asymmetric auxiliary 1042 reacts with styrene and sodium azide to generate azide 1043 in 90% yield and 94% diastereomeric purity. The following reaction (Scheme 172) with dimethyl acetylenedicarboxylate converts azide 1043 into triazole 1044 in 75% yield. Finally, the bond with selenium is cleaved by treatment with triphenyltin hydride and AIBN to furnish triazole 1045 in 80% yield and preserved optical purity (94%) <2003AGE3131>. 

The synthesis of 4,5-disubstituted triazoles shown in Scheme 208, carried out on a polymer support with microwave assistance, is based on a similar principle. In the first step, sulfinate 1248 is converted to sulfone 1249. Condensation with aldehydes provides vinyl sulfones 1250. Cyclocondensation of sulfones 1250 with sodium azide generates corresponding triazoline intermediates that eliminate sulfinate 1248 to provide triazoles 1251 in moderate to good yield <2006OL3283>. 

Azides 1253 obtained from propargyl halides or sulfonates 1252 undergo sigmatropic rearrangement to azidoal-lenes 1254, which subsequently undergo cyclization to triazafulvenes 1255. Under the reaction conditions, species 1255 react with another molecule of sodium azide to furnish triazoles 1256. Products 1256 are isolated in 65-97% yield (Scheme 209) <2005S1514>. 

From Sodium Azide and Vinylphosphonium Salts Phosphonium salts of the types 4 and 5 react with sodium azide in aqueous solution to give v-triazoles in high yield. The proposed mechanism (Scheme 13) involves nucleophilic attack at the carbon jS-tothe phosphorus, followed by cyclization with displacement of triphenyl-phosphine. 

Sodium azide also adds to olefins of this t3rpe to give w-triazoles in fairly good yields. A mechanism involving nucleophilic displacement of the substituent X by azide, followed by cyclization of the vinyl azide in the presence of azide ions, has been suggested. An alternative mechanism involves conjugate addition of azide to the double bond, cyclization of the resulting anion, and aromatization. 

Boyer and Gunasekaren reported the synthesis of the furazan-based heterocycle NOTO (44), which contains 50 % by mass of nitrogen and is a liquid at room temperature. The flve-step synthesis of NOTO (44) starts from the diazotization of 4,4 -diamino-3,3 -azoxyfurazan (DAAF) (27), followed by reaction with sodium azide to form the diazide (42). Heating the diazide (42) as a solution in acetonitrile induces cyclization to the triazole (43) and this is followed by reduction and oxidation of the remaining azide group to complete the synthesis of NOTO (44). 

Baryshnikov and co-workers synthesized some nitro-substituted 1,2,3-triazoles using an ingenious cycloaddition reaction between sodium azide and 1,1-dinitroethene the latter prepared in situ from a number of precursors including 2,2-dinitroethyl acetate (Section 1.10.2.3). 

Amino-5-nitro-1,2,3-triazole (ANTZ) (130), an explosive showing high thermal stability, has been synthesized via this route the reaction of sodium azide, acetaldehyde and 2,2-dinitroethyl acetate forming 4-methyl-5-nitro-1,2,3-triazole, which on conversion of the methyl group to an amino group yields ANTZ (130). Treatment of ANTZ (130) with hydrogen peroxide in sulfuric acid yields 4,5-dinitro-1,2,3-triazole (DNTZ) (131). 

Baryshnikov and co-workers used the same methodology for the synthesis of 5,5 -dinitro-4,4 -bis( 1,2,3-triazole) (133) (DNBT) from l,l,4,4-tetranitro-2,3-butanediol diacetate (132) in the presence of sodium azide. 

The tetrazole procedure that has been proved to be of value in the thiazolo[3,2-6][l,2,4]triazole series (see Section VIII) has also been applied in this field. V-Acylated 2-aminothiadiazoles 193 on treatment with phosphorus pentachloride (120°C) and subsequently with sodium azide (aqueous acetone) yield tetrazoles 194. Thermolysis in tetraline (160-180°C) gives the heterocycles 195 in moderate yields [85IJC(B)908 WFA953]. 

Junjappa and co-workers (9) reported the cycloaddition of sodium azide to the polarized ketene-(5,5)-acetal 33 to give the tiiazole 35 they also reported an intermolecular cycloaddition of tosyl azide 37 with the enamine 36 to give an unstable triazoline intermediate 38. Ring opening 38 followed by a Dimroth rearrangement afforded the triazole 41 (Scheme 9.9). 

Zinc chloride-doped natural phosphate was shown to have catalytic behavior in the 1,3-dipolar cycloadditions of nucleoside acetylenes with azides to form triazolonucleosides <99SC1057>. A soluble polymer-supported 1,3-dipolar cycloaddition of carbohydrate-derived 1,2,3-triazoles has been reported <99H(51)1807>. 2-Styrylchromones and sodium azide were employed in the synthesis of 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles <99H(51)481>. Lead(IV) acetate oxidation of mixed bis-aroyl hydrazones of biacetyl led to l-(a-aroyloxyarylideneamino)-3,5-dimethyl-l,2,3-triazoles <99H(51)599>. Reaction of 1-amino-3-methylbenzimidazolium chloride with lead(fV) acetate afforded l-methyl-l/f-benzotriazole <99BML961>. Hydrogenation reactions of some [l,2,3]triazolo[l,5-a]pyridines, [l,2,3]triazolo[l,5-a]quinolines, and [l,2,3]triazolo[l,5-a]isoquinolines were studied <99T12881>. 

Vicinal diazides 85a-c, prepared by the action of sodium azide on the corresponding 3,4-dichloromaleimide, react with triphenylphosphine in refluxing dichloromethane to give 2-amino-l,2,3-triazole derivatives 86a-c (Scheme 9). The stable di-Staudinger side products 87a-c are also produced from the reaction <2005JCX385>. 

The triazole ring can be synthesized by reaction between a suitable pyridine (or piperideine) and an azide. Thus 5-nitro-2-pyridone (or N-substituted pyridones) and sodium azide give a 5-oxotriazolo[4,5-b]pyridine (94)182-184 whereas the enamine 95 reacts with p-nitrophenyl azide to give the hexahydro-l//-triazolo[4,5-c]pyridine 96.185,186... 

Sodium azide in DMSO with ethyl propiolate and DMAD gave the triazoles 208 (R = H and E) together with small quantities of 1 2 adducts that tentatively were assigned structures 209 (R1 = H and E).159... 

Reaction of vinyl phosphonium salts with sodium azide also yields triazoles via triazoline intermediates by elimination of triphenylphosphine (Scheme 130).418... 

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