Derivatives of Benzotriazole

All reactions of benzotriazole derivatives of the type Bt-CR RbS discussed above are based on electrophilic or nucleophilic substitutions at the ot-carbon, but radical reactions are also possible. Thus, the first report on unsubstituted carbon-centered (benzotriazol-l-yl)methyl radical 841 involves derivatives of (benzotriazol-l-yl)methyl mercaptan. 3 -(Benzotriazol-l-yl)methyl-0-ethyl xanthate 840 is readily prepared in a reaction of l-(chloromethyl)-benzotriazole with commercially available potassium 0-ethyl xanthate. Upon treatment with radical initiators (lauroyl peroxide), the C-S bond is cleaved to generate radical 841 that can be trapped by alkenes to generate new radicals 842. By taking the xanthate moiety from the starting material, radicals 842 are converted to final products 843 with regeneration of radicals 841 allowing repetition of the process (Scheme 134). Maleinimides are also satisfactorily used as radical traps in these reactions <2001H(54)301>. 

Note No higher nitrated derivs of Benzotriazol-ols were found in Beil or in CA thru 1956... 

Deaminomethylation of Mannich bases may also occur in the presence of electrophilic species, capable of replacing the aminomethyl group linked to the substrate moiety, such as, for example, diazonium salts acting on Mannich bases of phenols and indoles, or alcohols acting on cyclic O-Mannich bases. The deaminomethylation reaction is also prc.sent in. several equilibria afforded by aminomethyl derivatives of benzotriazole (sec 209, Chap. 1, C.6). 

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. 

Potentially, nitroxides can convert into phenoxyls other stabilizers containing phenolic moieties, e.g. phenolic derivatives of benzotriazole or 2-hydroxybenzophe-nones. 

Effective UVAs are required to have absorption maxima lying between 300 and 380 nm, preferably between 330 and 350 nm, and an inherent photostability. Various UVAs, including derivatives of benzotriazoles, 1,3,5-triazines, and oxanilides, fulfil these requirements and are, therefore, widely applied in coatings [87]. 

Nitrite can be oxidized to nitrate and determined as nitrobenzene, but several alternative derivatizat-ion techniques have been developed. Nitrate can be converted into tetrazolophthalazine or the trim-ethylsilyl derivative of benzotriazole, or the ion can be derivatized with 3,4-dichlorobromobenzene or p-bromochlorobenzene by the Sandmeyer reaction. An elegant one-step derivatization procedure involves the reaction of pentafluorobenzyl bromide with nitrite in alkali at 50°C for 90 min. This procedure allows analysis with an electron-capture... 

Among the many organic compounds recently proposed for the photostabilization of polymers, derivatives of benzophenone, complex esters of salicyclic acid, derivatives of benzotriazole, various organic tin compounds, thlazolidones, etc. are finding use. The last two classes of compounds are not considered in this chapter, since the methods of synthesis, properties, and use of organic tin compounds [1, 2] and thiazo-lidones [3, 4] have been rather fully treated in the literature. 

Exposure of the molded HDPE articles to sunlight and air also attacks the polymer over time, especially at wavelengths less than 400 nm. Photooxidation resembles thermooxidation in that it is a complex chain of radical transformations. Such exterior aging of the polymer results in development of surface cracks, brittleness, changes in color, and a deterioration of mechanical and dielectrical properties. Photooxidation degradation is prevented by small amounts of light stabilizers, such as 2-4% carbon black or, for colorless articles, esters of salicylic acid or derivatives of benzotriazole or benzophone and others in the 0.1-0.5% range. 

Recently click-chemistry approach to the preparation of fluorobenzo-fused 1,2,3-triazole 137 was demonstrated in the paper of Larock et al. [119], Zhang and Moses developed a special version of one-pot click-chemistry for the preparation of monofluoro derivatives of benzotriazole 138, 139 from p-methoxyaniline and o-fluoroanthranilic acid with two in situ generated intermediates p-methoxyphenyl azide and fluorobenzyne [120],... 

Stabilization against UV can be achieved by UV absorbers such as derivatives of benzotriazoles and benzophenones, and by hindered amine light stabilizers (HALS). For more details, see [247]. 

A. Dubey S.K. Srivastava, S.D. Srivastava, Conventional and microwave assisted synthesis of 2-oxo-4-substituted aryl-azetidine derivatives of benzotriazole a new class of biological compormds, Bioorg. Med. Chem. Lett. 21 (2011) 569-573. 

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