Benzotriazoles, 1-substituted

Ultraviolet absorbers continue to be the most widely used stabilizers. Such products must have long-term stability to ultraviolet light, be relatively nontoxic, heat stable, have little color, must not sensitize the substrate, and must be priced at levels which the plastics processor can tolerate. The principal classes of chemicals meeting these requirements at present are the 2-hydroxybenzophenones, and 2-(2/-hydroxyphenyl)benzotriazoles, substituted acrylates, and aryl esters. Typical compounds representative of these classes are 2-hydroxy-4-octoxybenzophenone, 2-(2 -hy droxy-5 -me thylphenyl) be nzotn azole, ethyl-2-cyano-3,3-diphenyl acrylate, diinethyl / -methoxybenzylidene maJonate, and / -ter -octylphenyl salicylate. 

Meier and co-workers synthesized thieta[ naphthalene 47 in 58% yield by FVP of a benzotriazole-substituted naphthalene <1998JHC1505>, together with cyanocyclopentadiene as a side product (Equation 27). 

Treatment of the solid-supported amino acetals (529) with catalytic PTSA, followed by addition of IH-benzotriazole, resulted in the 2-benzotriazole-substituted piperidines (530) as stable N-acyliminium ion precursors, according to Katritzky [392]. A number of different carbon nucleophiles were then added to the N-acyliminium ions, generated under acid catalysis by either boron trifluoride etherate or camphorsulfonic acid (Scheme 107). 

A number of polymerizable ultraviolet stabilizers have been synthesized and their homo- and copolymerization studied. The initial work consisted of the synthesis of vinyl derivatives of methyl salicylate (three isomers), 2, -dihydroxy-benzophenone, and ethyl a-cyano-p-phenylcinnamate. More recently, vinyl derivatives (two isomers) and one isopro-penyl derivative of 2(2-hydroxyphenyl)2H-benzotriazole have been prepared. A number of benzotriazoles with more than one benzotriazole ring in the molecule, or compounds with both benzo(or aceto)phenone and 2(2-hydroxyphenyl)2H-benzo-triazole groups in one molecule, have also been synthesized. Acryloyl and methacryloyl derivatives of benzotriazole-substituted polyphenols have been prepared and homo- and copolymerized. 

Phosphoranylideneaminoquinones, e.g. (20), have been prepared in good to excellent yields by the reaction of phosphines with [2,l]benzisoxazole-4,7-quinones, e.g. (19)." A safer alternative to the vinyl azide-based synthesis of (N-vinylimino)phosphoranes (21) has been reported (Scheme 1)." N-(AlkyIthiomethyl)iminophosphoranes (23) have been synthesised from the benzotriazole-substituted iminophosphorane (22) and used without isolation to provide routes to N-alkylthiomethyl-imines, -amides, and -ureas. Tetraazolyl-substituted ylides (25) and (26) are the products of the reaction of vinylphosphonium salts (24) with excess sodium azide." The novel 1,2-1 -azaphosphete (28), which is potentially antiaromatic, has been prepared by the reaction of the azide... 

Katritzky, A. R., Steel, P. J., Denisenko, S. N. (2001). X-Ray Crystallographic Evidence for a Vinylogous Anomeric Effect in Benzotriazole-substituted Heterocycles. Tetrahedron, 57,3309-3314. 

Due to their dissymmetry, benzotriazoles substituted in the benzene part show three tautomers. In solution, the equilibria are positioned almost entirely on the side of the IH-form [503]. Although the 2H-tautomers possess an orthoquinonoid structure, NMR-spectra of 2-methylbenzotriazole indicate large 7t-delocalization (comparable to the case of 2-methylindazole, cf. p. 244). 

Substances satisfying these conditions are colorless and do not absorb in the high-wavelength range. It is possible to classify them according to their chemical structure as derivatives of 2-hydroxybenzophenone, esters of aromatic acids and aromatic alcohols, hydroxyphenyl-benzotriazoles, substituted acrylonitriles, metallic complexes (excited-state quenchers), and inorganic pigments [4,9,23,26,27]. 

Five main groups of chemical compounds show sufficient protective activity to be commercially important substituted 2-hydroxy phenyl benzotriazoles, substituted 2-... 

Annular tautomerism (e.g. 133 134) involves the movement of a proton between two annular nitrogen atoms. For unsubstituted imidazole (133 R = H) and pyrazole (135 R = H) the two tautomers are identical, but this does not apply to substituted derivatives. For triazoles and tetrazoles, even the unsubstituted parent compounds show two distinct tautomers. Flowever, interconversion occurs readily and such tautomers cannot be separated. Sometimes one tautomeric form predominates. Thus the mesomerism of the benzene ring is greater in (136) than in (137), and UV spectral comparisons show that benzotriazole exists predominantly as (136). 

Treatment of the substituted azobenzene (561) with triethyl phosphite gave the triazapen-talene (563). It is likely that the 2-substituted benzotriazole (562) was initially formed which then underwent deoxygenative cyclization to (563) (74CL951). 

Particular attention has been given to the study of thermal rearrangements of N-substituted benzotriazoles. N-(N, N -Dialkylaminomethyl) benzotriazoles exist in the solid state solely as the isomers 37a, but in the liquid, solution, melt, and argon matrix phases they form equilibrium mixtures of the tautomers 37a and 3 (Scheme 19) [76JCS(P2)741 ... 

When reacted with dimethyl acetylenedicarboxylate, the amines produced ben-zotriazolylaminobutendioates 188 accompanied by A-benzotriazolyl substituted 2-pyridones only in the case of 5-amino-2-methyl-2//-benzotriazole, the triazolo-9,10-dihydrobenzo[d]azepine and an unusual cyclization product, triazolo-2-oxindole (convertible into 2-methyltriazolo[4,5-/]carbostyril-9-carboxylate) were formed. The quinolones 189 were aromatized to chloroesters 190 these in turn were hydrolyzed to chloroacids 191 and decarboxylated to 9-chlorotriazolo[4, 5-/]quinolines 192 (Scheme 58) (93H259). The chlorine atom could be replaced with 17 various secondary amines to give the corresponding 9-aminoalkyl(aryl) derivatives 193, some of which exhibit both cell selectivity and tumor growth inhibition activity at concentrations between 10 and 10 " M (95FA47). 

Michael additions of benzotriazole-stabilized carbanions 98CCC599. Properties and synthetic utility of N-substituted benzotriazoles 98CRV409. 

Reaction of 2-[(benzotriazol-l-yl)alkylamino]pyridines 341 with open-chain electron-rich alkenes 342 in the presence of BF3-Et20 gave 4-substituted 1,2,3,4-tetrahydropyrido[l, 2-n]pyrimidinium tetrafluorobo-rates 343 (98S704). 

A-Substituted 11-oxo-l l//-pyrido[2,l-6]quinazoline-6-carboxamides were prepared from 11-oxo-l l//-pyrido[2,l-6]quinazoline-6-carboxylic acids and amines in the presence of (/-Pr)2EtN and benzotriazol-l-yloxytris(dimethy-lamino)phosphonium hexafluorophosphate in CH2CI2 (98MIP1, 98MIP2, 99USP5908840, 99USP5914327). 

A few aromatic amines do not react e.g. -substituted diamines yield benzotriazoles that cannot couple [1]. 

Ethoxycaibonylation of the 7-methylpyrrolotetrazolide ion gave the Nl-substituted product 18 preferentially <96JOC5646>. The 1,3-dipolar cycloaddition reactions of 19 with alkenes was investigated <96JHC335> as was the formation and reactivity of the tetrazoyl(benzotriazol-l-yl)methane 20 <96JHC1107>. 

The compounds referred to as azolides are heterocyclic amides in which the amide nitrogen is part of an azole ring, such as imidazole, pyrazole, triazole, tetrazole, benzimidazole, benzotriazole, and their substituted derivatives. In contrast to normal amides, most of which show particularly low reactivities in such nucleophilic reactions as hydrolysis, alcoholysis, aminolysis, etc., the azolides are characterized by high reactivities in reactions with nucleophiles within the carbonyl group placing these compounds at about the same reactivity level as the corresponding acid chlorides or anhydrides. 11... 

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>. 

A one-pot reaction between a tryptophan ester, benzotriazole, and 2,5-dimethoxytetrahydrofuran in acetic acid gives the diastereomeric benzotriazolyl tetracycles, 349, in good yield. Substitution of the benzotriazole by reaction with silyl enol ethers and boron trifluoride etherate gives the corresponding ketones 350 and 351, and reaction with allylsilanes gives the corresponding alkenes 352 and 353. If the boron trifluoride etherate is added to the mixture before the silane, elimination of benzotriazole from 349 is also observed (Scheme 83) <1999T3489>. 

Some interesting fused 1,2,3-triazole ring systems have been reported. A series of 5-piperidyl-substituted 7-hydroxy-3f/-l,2,3-triazolo[4,5-d]pyrimidines 143 has been synthesized from pipecolinate esters, benzylazides, and cyanoacetamide <06CHE246>. 4-Alkylidene-5,6-dihydro-4//-pyrrolo-[l,2-c][l,2,3]triazoles 144 were prepared from alkylidenecyclopropanes via diiodogenation/Cu(I)-catalyzed 1,3-dipolar cycloaddition/intra-molecular Heck reaction sequence <06SL1446>. 6,6-Dimethyl-2-phenyl-4,5,6,7-tetrahydro-27/-benzotriazol-4-one 145 were prepared from A-(5,5-dimethyl-3-oxocyclohexenyl)-S,S-diphenylsulfilimine and... 

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