1//-Benzo triazole

In peptide syntheses, where partial racemization of the chiral a-carbon centers is a serious problem, the application of 1-hydroxy-1 H-benzotriazole ( HBT") and DCC has been very successful in increasing yields and decreasing racemization (W. Kdnig, 1970 G.C. Windridge, 1971 H.R. Bosshard, 1973), l-(Acyloxy)-lif-benzotriazoles or l-acyl-17f-benzo-triazole 3-oxides are formed as reactive intermediates. If carboxylic or phosphoric esters are to be formed from the acids and alcohols using DCC, 4-(pyrrolidin-l -yl)pyridine ( PPY A. Hassner, 1978 K.M. Patel, 1979) and HBT are efficient catalysts even with tert-alkyl, choles-teryl, aryl, and other unreactive alcohols as well as with highly bulky or labile acids. 

Benzoate can be used as an anodic inhibitor and is effective at preventing waterline attack. Phosphate is also sometimes included. Sodium borate (borax) is usually added to the formulation to provide an alkalinity reserve buffer. Typically, a copper inhibitor such as benzo-triazole (BTA) or tolyltriazole (TTA) also forms part of a formulation and is used to provide yellow metal (copper and brasses) protection. 

PM 60320 70321-86-7 Tinuvin 234 2-(2-Hydroxy-3,5-bis(l, 1 -dimethylbenzyl)-phenyl)benzo-triazole... 

More recently, Somfai and coworkers have reported on the efficient coupling of a set of carboxylic acids suitable as potential scaffolds for peptide synthesis to a polymer-bound hydrazide linker [24]. Indole-like scaffolds were selected for this small library synthesis as these structures are found in numerous natural products showing interesting activities. The best results were obtained using 2-(7-aza-l H-benzo-triazol-l-yl)-l,l,3,3-tetramethyluronium hexafluoride (HATU) and N,N-diisopropyl-ethylamine (DIEA) in N,N-dimethylformamide as a solvent. Heating the reaction mixtures at 180 °C for 10 min furnished the desired products in high yields (Scheme 7.4). In this application, no Fmoc protection of the indole nitrogen is required. 

For clarity, in the following schemes of this subsection, the benzotriazol-2-yl stmctures are often omitted when such derivatives are present in the reaction mixtures, and their chemistry is not different from that of the benzo-triazol-l-yl derivatives. When there is a clear distinction in chemistry, the benzotriazol-2-yl isomers are treated separately. 

Condensation of benzaldehydes with benzotriazole in the presence of thionyl chloride readily gives a,a-/fe(benzo-triazol-l-yl)toluenes 727 that can be considered as l,l -gm-dicarbanion equivalents. Thus, treatment of derivatives 727 with ketones and lithium metal suspended in THF at — 78 °C generates substituted propylene glycols 728 (Equation 18) <1998TL2289>. 

Due to its wide application in peptide synthesis, 1-hydroxybenzotriazole 1001 is the most commonly used benzo-triazole derivative with hundreds of references in Chemical Abstracts each year. Utility of compound 1001 comes from its readiness to form esters with carboxylic acids in the presence of dehydrating agents (DAs). Obtained esters 1002 react eagerly with amines to produce amides 1003 in high yields (Scheme 165). More details about this application are given in Section 5.01.12. 

Substituents at the C(4) and C(5) positions of 1,2,3-triazole and at the benzene ring of benzo-triazole can undergo normal functional transformations which are independent of the triazole ring. In addition, these substituents can undergo some specialized reactions, particularly the formation of triazolo fused bi- and tricyclic systems. 

The diazotization of o-diaminobenzene derivatives is the most common synthetic route to benzo-triazoles. Triazolo[6,7- /]phthalide (791) is synthesized in a seven-step sequence from phthalide in 24% overall yield as shown in Scheme 159. Triazolo[6,7-c ]dihydrocoumarin is similarly prepared in nine steps from dihydrocoumarin in 20% overall yield <92JHC1519>. Benzo[l,2-tf 4,5-tf jbistriazole (795) is synthesized from w-dichlorobenzene in five steps and 54% overall yield (Scheme 160). The hydrogenation of (792) is carried out in ethanol to give (793), which, without isolation, is diazotized at 0°C to afford diacetyl bistriazole (794) in 96% yield <86JOC979>. 

Das in der Peptidchemie bewahrte Kopplungsreagenz 1-Triphenylphosphonionooxy-benzo-triazol-hexafluorophosphat liefert mit einem Hexulosonsaure-Derivat zunaebst das Amid, das ohne weitere Reinigung thermisch zu l-C-(2-Benzimidazolyl)-l,2 3,4-di-O-isopropyli-den-fi-D-arabino-pentopyranose (75% Schmp. 210°) cyclisiert230. 

When 0,(y-diazidoazobenzene (10) is heated, nitrogen is liberated in two distinct stages one mole at the surprisingly low temperature of 58° yielding 2-(o-azidophenyl>2H-benzo-triazole (11) and the second mole at approximately 17Gl0 to give dibenzo-1,3a,4,6a-tetraazapentalene (12).1H 1M It seems quite reasonable that 11 is formed by a concerted process and 12 by a nitrene intermediate. 

From a- or 0- substituted aldehydes or ketones by elimination reactions Benzeneselenenyl trichloride, 27 Methanesulfonyl chloride-4-Di-methylaminopyridine, 176 9-(Phenylseleno)-9-borabicyclo-[3.3.1]nonane, 245 By oxidation of allylic substrates Pyridinium chlorochromate-Benzo-triazole, 262 By other methods Alumina, 14... 

Pentacarbonyl(methoxymethyl-methylene)chromium, 83 Phosphomolybdic acid-Potassium di-chromate-Copper(II) sulfate, 248 Pyridinium chlorochromate, 237 Pyridinium chlorochromate-Benzo-triazole, 262... 

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