Benzotriazoles, nitro derivatives

The initial stage of this reaction involves a nucleophilic halogen substitution followed by intermolecular redox cyclization of ort/zo-nitrohydrazobcnzcncs [642], Instead of halogen the substrate can contain another group (N02, OAlk) [643-645], It has been shown that in ethanol the aforementioned reaction proceeds with the formation of 2//-benzotriazole nitro derivatives, whereas in acetic acid their IV-oxides are formed and, when boiled in ethanol, turn into the final products (Scheme 2.123) [637, 638, 646],... 

Nitration of a series of mesomeric betaines was extensively studied in connection with their potential use as explosives (Scheme 3). Nitration of l,2,3-triazolo[2,l- ]benzotriazole 74 can be achieved selectively, occurring first at the 7-position which is followed by nitration at the 3- and 5-positions. Thus, nitration with 45% nitric acid gives a mixture of 7-nitro derivative 75 (39%) and dinitro derivative 76 (58%), while 70% nitric acid yields a mixture of 3,7- (52%), 5,7- (23%), and 3,5-dinitro (5%) isomers 76-78. Clean trinitration to 3,5,7-trinitro-l,2,3-triazolo[2,l- ]benzotriazole 79... 

To get a complex set of substituents by direct derivatization of benzotriazole is not feasible. In such situations, it is better to have all the substituents in place first and later construct the heterocyclic ring. High reactivity of anilines and their well-developed chemistry makes them good stating materials. In an example shown in Scheme 215, acetanilide 1288 is nitrated to afford nitro derivative 1289 in 73% yield. Catalytic reduction of the nitro group provides methyl 4-acetylamino-3-amino-5-chloro-2-methoxybenzoate 1290 in 96% yield. Nitrosation of compound 1290 in diluted sulfuric acid leads to intermediate 1291, which without separation is heated to be converted to 7-chloro-4-methoxy-l//-benzotriazole-5-carboxylic acid 1292, isolated in 64% yield <2002CPB941>. 

Trinitrotoluene (TNT), Picric Acid (PA), Triaminotrinitrobenzene (TATB), hexanitrostilbene (HNS), 2,4,6-(trinitrophenyl)methynitramine (Tetryl), 1,3,7,9-6H-benzotriazolo[2,l-a]benzotriazol-5-ium (TACOT) and their higher order nitro derivatives, are important nitroaromatic explosives. One of the competing initial steps in the detonation of these nitroaromatics has been shown to involve... 

So-called Kyodai nitration - a novel methodology of nitration with nitrogen dioxide and ozone - has been applied to several benzimidazoles with formation of 1-nitrobenzimidazoles and following conversion to 1-nitrobenzotriazoles [275], The nitration of benzotriazole /V-oxide with dilute nitric acid gives the 7-nitro derivatives, whereas nitration with a mixture of nitric and acetic acids leads to 5-nitro- and 7-nitro isomers in a ratio of 1 9 [276],... 

The VNS is the reaction of choice for incorporation of a-sulfonylalkyl substituents into nitroarenes and their heteroanalogues. Particularly accessible and useful are nitroarylmethyl phenyl sulfones and their heteroanalogues that are efficiently produced in the VNS reactions of carbanions of chloromethyl aryl sulfones with a great variety of nitroarenes and nitroheteroarenes. Nitro derivatives of heterocycles, such as pyrrole [54,55], furan [54], thiophene [54], imidazole [106, 112, 113], pyrazole [114], pyridine [57], indole [115], indazole [116, 117], benzimidazole [118], benzotriazole [119], benzofuroxan [120], quinoline [121], and porphyrins [122, 123], have been shown to enter this reaction. 

Tetranitro derivative 90 (z-TACOT Section 12.10.15.5) treated with methanolic sodium methoxide at ambient temperature does not lead to simple product of nucleophilic substitution of a nitro group but provides compound 92. Its formation can be rationalized by introduction of the methoxy group into the 1-position, followed by scission of the remote triazole ring of 91 to give the final product. Compound 90 subjected to the vicarious nucleophilic substitution (VNS) conditions using either hydroxylamine or trimethylhydrazinium iodide gives a very insoluble red solid, which was identified as l,3,7,9-tetraamino-2,4,8,10-tetranitrobenzotriazolo[2,l- ]benzotriazole 93 (Scheme 5) <1998JOC3352>. 

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>. 

A series of /> ra-substituted ort o-nitroanilines 1274 is converted in this way to benzotriazolyl derivatives 1277, which are of interest as potassium channel activators. In the first step, nitroanilines 1274 are treated with salicylyl chloride to provide salicylamides 1275 in 70-95% yield. The nitro group is catalytically reduced, and the obtained intermediates 1276 are subjected to a reaction with nitrous acid, generated in situ from NaN02, to afford 5-substituted T(2-hydroxybenzoyl)-17/-benzotriazoles 1277 in 52-96% yield (Scheme 213) <2001FA827>. 

Only a limited range of nitro, azo and anthraquinone disperse dyes exhibit adequate fastness to dry heat, light and weathering for application on polyester automotive fabrics. The structure of Cl Disperse Yellow 86 was modified to incorporate UV absorbers of the benzophenone, benzotriazole or oxalanilide types into the dye molecule. The derived dyes showed better fastness properties than the parent unsubstituted dye. Positioning of the photostabilising moiety within the dye molecule had little influence on the light fastness obtained, however. Built-in benzophenone residues were more effective than the other two types [177]. Nevertheless, several further monoazo and nitrodiphenylamine disperse dye... 

PVC, polyamides, unsaturated crosslinked polyesters, ABS, and wood . Di- and tri-benzotriazole photostabilizers, such as (874) and (875) are synthesized from 2-nitro-benzenediazonium salts and an excess of 1,3-dihydroxybenzene or 1,3,5-trihydroxybenzene <85Mi 40i-0l>. The dibenzotriazole derivatives (874b and 875b) can be used as polymerizable acrylic UV absorbers <84PB237>. A few or/Ao-urethane and -trimethylsilane substituted 2-phenylbenzotriazoles (876 and 877) show similar photostabilization activity . Weather resistance of low-density polyethylene is improved by the addition of a benzotriazole-type photostabilizer <90M140i-04>. 

Because of the enhanced electrophUidty of the amidine carbon in A,A -bis(alkoxycarbon-yl)carboximidamide derivatives, the A,A -bis(fert-butoxycarbonyl)-l//-benzotriazole-l-carboximidamide and A(A -bis(ferf-butoxycarbonyl)-6-nitro-l//-benzotriazole-l-carboximid-amide derivatives were proposed. The latter compound proved to be the most reactive guanidinylating reagent for sterically hindered amines in solution and on solid support. 

N-Benzotriazole derivatives of quinine and quinidine were applied as phase-transfer catalysts for the nitro-Mannich reaction between a-amido-sulfones and nitroalkanes (Scheme 6.57) [119]. The products were formed in good yields and high enantioselechvihes and could be transformed efficiently into either a diamine... 

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