Benzotriazole 1 -cyano

A similar approach, synthesis of a selectively substituted benzotriazole from the corresponding ortfe-nitroaniline, is depicted in Scheme 212. The process starts from a microwave-assisted substitution of the fluorine atom in 4-fluoro-3-nitrobenzonitrile 1270 by isopropylamine to give ortfo-nitroaniline 1271 in 99% yield. Reduction of the nitro group provides ortfo-phenylenediamine 1272 that is directly converted to 5-cyano-l-isopropylbenzotriazole 1273, which is isolated in 83% yield <2006JME1227>. 

Benzotriazole reacts with l-cyano-4-dimethylaminopyridinium bromide to give 1-cyano-benzotriazole (177) (Scheme 29) <88S470>. 1-Cyanobenzotriazole is also prepared in a more convenient way from cyanogen bromide and the sodium salt of benzotriazole in 90% yield under carefully controlled conditions <91RRC573>. Benzotriazole can be chlorinated at the N(l) position by NaOCl <85H(23)2225>. A-Fluorination of benzotriazole with caesium fluoroxysulfate gives 1-fluorobenzotriazole in 25% yield <91T7447>. 

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. 

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. 

Typical, ultraviolet absorbers are salicylate esters, -amino-benzoate esters, a-cyano-0-phenylcinnamate esters, 2-hydroxybenzo-phenones, 2(2-hydroxyphenyl)2H-benzotriazoles (Figure 1), and more recently diaminodiphenyloxamides. Some pigments and various types of carbon blacks are also known as effective ultraviolet stabilizers. Another mechanism by which the stabilization of the polymers can be accomplished is by quenching the excited state of the molecules. 

Rather than using benzotriazole as an anion-stabilizing group, Da, Junjappa, and their coworkers employed a cyano group to effect an indole ring synthesis (Schane 7, equation 1) [39]. Attempts to isolate addnct 5 were unsnccessful as it slowly underwent indolization npon silica gel chromatography. Raney nickel desulfurization also converted the indole products 6 to the corresponding 7-methylindoles (85%-94%... 

UVA 2-hydroxy-4-octyloxybenzophenone 2-hydroxy-4-methoxybenzophenone 2-(2H-benzotriazol-2-yl)-p-cresol 2-(2H-benzotriazole-2-yl)-4,6-di-tert-pentylphenol 2-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetraethylbutyl)phenol 2,4-di-tert-butyl-6-(5-chloro-2H-benzotriazole-2-yl)-phenol 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-(octyloxy) phenol ethyl-2-cyano-3,3-diphenylacrylate HAS 1,3,5-tri-azine-2,4,6-triamine, N,N [1,2-ethane-diyl-bis[[[4,6-bis[butyl-(1,2,6,6-pentamethyl-4-piperidinyl)amino]-1,3,5-triazine-2-yl] imino]-3,1 -propanediyi] bis[N ,N -dibutyl-N ,N -bis(1,2,2,6,6-pentamethyl-4-piperidinyl)- bis(2,2,6,6-tetramethyl-4-piper-idyl) sebacate 2,2,6,6-tetramethyl-4-piperidinyl stearate N,N -bisformyl-N,N -bis-(2,2,6,6-tetramethyl-4-piperidinyl)-hexamethylendiamine alkenes, C20-24-.alpha.-, polymers with maleic anhydride, reaction products with 2,2,6,6-tet-ramethyl-4-piperidinamine 1,6-hexanediamine, N, N -bis(2,2,6,6-tetramethyl-4-piperidinyl)-, polymers with 2,4-di-ohloro-6-(4-morpholinyl)-1,3,5-triazine 1,6-hexanediamine, N,N -bis(2,2,6,6-tetramethyl-4-piperidinyl)-, polymers with morpholine-2,4,6-trichloro-1,3,5-triazine reaction products, methylated Phenolic antioxidants ethylene-bis(oxyethylene)-bis(3-(5-tert-butyl-4-hydroxy-m-tolyl)-propionate) 2,6,-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5,-triazine-2-ylamino) phenol pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate) 2-(1,1 -dimethylethyl)-6-[[3-(1,1 -dimethylethyl)-2-hydroxy-5-methylphenyl] methyl-4-methylphenyl acrylate isotridecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate 2,2 -ethylidenebis (4,6-di-tert-butylphenol) 2,2 -methylenebis(4-ethyl-6-tertbutylphenol) 3,5-bis(1,1-dimethyethyl)-4-hydroxy-benzenepropanoic acid, C13-15 alkyl esters phenol, 4-methyl-, reaction products with dicyclopen-tadiene and isobutene Phosphite trinonylphenol phosphite isodecyl diphenyl phosphite... 

UVA 2,4-dihydroxybenzophenone 2-(2H-ben-zotriazol-2-yl)-p-cresol phenol, 2-(5-chloro-2H-benzotriazole-2-yl)-6-(1,1 -dimethylethyl)-4-methyl- 2-(2H-benzotriazole-2-yl)-4,6-di-tert-pentylphenol 2-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetraethylbutyl)phenol 2-(2H-benzotriazol-2-yl)-4,6-bis(1 -methyl-1 -phenylethyl)phenol 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol, branched linear 2,4-di-tert-butyl-6-(5-chloro-2H-benzotriazole-2-yl)-phenol reaction product of methyl 3(3-(2H-benzotriazole-2-yl)-5-t-butyl-4-hydroxyphenyl propionate/PEG 300 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-(octyloxy) phenol (2-ethylhexyl)-2-cyano-3,3-diphenylacrylate HAS ... 

UV absorbers (Figure 5.20) are organic compounds that absorb harmful UV light and dissipate the absorbed energy as harmless thermal energy. Important classes of UV absorbers are 2-hydro-xybenzophenones, benzotriazoles, hydroxyphenyl-s-triazines, and oxalanilides. Some other compounds such as hydroxyphenylpyrimi-dines, salicylic acid derivatives and cyano acrylates are also useful. 

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