1 -Chlorobenzotriazole chlorination

The perimidines should be A-substituted to avoid oxidation. With A-chlorobenzotriazole, chlorination leads to a mixture of 4- and 9-chloro derivatives. With 2 equivalents the 4,9-dichloro derivative results. Subsequent chlorinations yield the 4,7,9-trichloro and the tetrachloro derivative. 

Of great importance was the discovery by Johnson et al. (185) of the stereospecific synthesis of optically active sulfonimidoyl chlorides, which are key substrates for making new types of sulfonimidoyl compounds. The method involves chlorination of readily available chiral sulfinamides with chlorine or A/-chlorobenzotriazole. Scheme 12 summarizes the synthesis of (-)-(/ )-A/-methylphenylsulfonimidoyl chloride 163 from (+HS>N-methyl benzenesulfinamide 164 and its reactions with sodium phenoxide and dimethylamine. 

A number of N-brominated and N-chlorinated heterocycles also provide sources of electrophilic bromine. Examples include 1-chlorobenzotriazole (82JOC4895 87JOC173 88CHE36) and various HBr and Br2 adducts of pyridines, or pyridine perbromides [84SC939 85JAP(K)60/87264], Polymer-supported reagents of this type include 1-cyclohexylpyridinium perbromide linked to polystyrene, effective for the bromination of 1-methylindole, benzo[fc]furan, and benzo[6]thiophene (89T7869). 

Benzotriazole can be chlorinated at the N(l) position by NaOCl (85H(23)2225). 1-Chlorobenzotriazole - a rather stable crystalline compound that has found application in organic synthesis as a selective chlorinating reagent and mild oxidant. A-Fluorination of benzotriazole with cesium fluoroxysulfate gives 1-fluorobenzotriazole in 25% yield (91T7447). 

The kinetics of the chlorination of phenol and 2-naphthol by l,3-dichloro-5,5-dimethylhydantoin (2) in aqueous acidic media have been interpreted10 in terms of an initial rate-limiting formation of a charge-transfer complex between the substrate and the chlorinating agent. A kinetic study of the chlorination of nine aryl ethers by 1-chlorobenzotriazole in acetic acid has also led to mechanistic conclusions.11... 

As initially reported by Greci and coworkers83 and later by Greci, Eberson and coworkers84, l-methyl-2-phenylindole (22) treated with A-chlorobenzotriazole (BT-CI, 23) is monochlorinated to 24 and also yields dimeric structures, some of which themselves are chlorinated and dichlorinated (equation 56). Product 27 was mentioned only in the more recent paper. The mechanism in equation 57 was suggested in the initial paper. The formation of products 25-28 was ascribed to the interaction between various substituted indole-radical cations and adventitious water in the medium. The later study confirmed that the substituted indole-radical cation 22a is an intermediate and that the formation of... 

Chlorination of indole alkaloids. Indole alkaloids of the type (1) on reaction with a 5-10% molar excess of 1-chlorobenzotriazole in dry methylene chloride or benzene are converted in high yield into chloroindoicnincs (2). r-Butyl hypochlorite has been u.scd previously for such conversions. Reported yields arc not so high as those obtained... 

The direct amination of benzotriazole by the use of HOSA was first reported in a patent (65USP3184471). The total yield of 1- and 2-amino-benzotriazoles, separated by crystallization, was not high (20%). Later, Rees and co-workers changes the conditions of amination and achieved yields of 38% and 11% for 1- and 2-amino derivatives, respectively [69JCS(C)742], Amination of the sodium salt of benzotriazole with chloroamine failed. An attempt to exchange the chlorine atom for the amino group in 1-chlorobenzotriazole under the action of sodium amide was also unsuccessful [69JCS(C)1474]. 

Most synthetic applications of benzotriazoles are based on the acceptor action of the benzotria-zol-l-yl moiety i.e. on the stability of the benzotriazolyl anion. For instance 1-chlorobenzotriazole is used as a chlorinating agent. It transfers a Cl ion to the substrate. An example of this reaction is the chlorination of carbazole in dichloromethane to give 3-chlorocarbazole. 1-Hydroxybenzotriazole is obtained by condensation of l-chloro-2-nitrobenzene with hydrazine ... 

Hydroxyphenyl benzotriazoles have the structure (XV) where X is H or Cl (chlorine shifts the absorption to longer wavelengths), Ri is H or branched alkyl, and R2 is CH3 to CgHi7 linear and branched alkyl (Ri and R2 increase the affinity to polymers). Some technically important materials in this class are 2-(2 -hydroxy-5 -methyl-phenyl)-benzotriazole, 2-(2 -hydroxy-3 -5 -(Ji.fert-butyl-phenyl)-benzotriazole, and 2-(2 -hydroxy-3, 5 -di-tert-butyl-phenyl)-5-chlorobenzotriazole. In comparison with 2-hydroxybenzophenones, the 2-(2 -hydroxyphenyl) benzotriazoles have higher molar extinction coefficients and steeper absorption edges towards 400 nm. 

Equimolar amounts of cyclohexanol and 1-chlorobenzotriazole warmed in methylene chloride until an exothermic reaction starts cyclohexanone. Y 70%. -The above new oxidant, a positive-chlorine compound, is potentially useful because of its easy prepn., stability, reactivity under mild conditions, and easy isolation of the products. F. e. and oxidations s. C. W. Rees and R. C. Storr, Chem. Commun. 1968, 1305 Soc. (C) 1969, 1474 S-oxygenations such as sulfoxides from thioethers s. W. D. Kingsbury and C. R. Johnson, Chem. Commun. 1969, 365. 

Chlorobenzotriazole is a convenient and highly efficient reagent for nuclear chlorination of carbazoles. - E Carbazole in methylene 9hloride mixed with 1 mole 1-chlorobenzotriazole in the same solvent, and allowed to stand overnight 3-chlorocarbazole. Y 79%. F. e. s. P. M. Bowyer, D. H. lies, and A. Ledwith, Soc. (C) 1971, 2775. 

Chlorobenzotriazole in didiloromethane added to a stirred soln. of deserpidine in the same solvent, and the product isolated after 15 min. 7-chloro-7H-deserpidine. Y 93.5%. F. e. s. K. V. Lidiman, Soc. (C) 1971, 2539 1-chlorobenzotriazole and 1,3-dichloro-l,2,4-triazole as chlorinating agents s. H. Oel-sdilager and E. Ehlers, Pharm. Acta Helv. 47, 1 (1972). 

For instance, 1-chlorobenzotriazole is used as a chlorinating agent It transfers a Cl ion to the substrate. An example is the chlorination of carbazole in dichloromethane to give selectively 3-chlorocarbazole. 

Caffeine 478, 479 Camptothecin 405 Cannabinol 345 Cantharidin 89 Carazolol 149 l,l -Carbonyldiimidazol 228 Carlina oxide 78 Capri Blue 446 e-Caprolactam see azepan-2-one Captopril 161 Carbamazepine 539 Carbazole 148, 149 Carbostyryl 387 Cardiazol see pentetrazole Catechin 340 Cefatrizin 264 Celecoxib 243 Cephalosporin 455 Cepham 455 Cerivastin 379 Chalciporon 539 Chelidonic acid 335 Chemiluminescence 55 1-Chlorobenzotriazole 267 Chlordiazepoxide 544 Chlorin 551... 

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