Benzotriazoles specials

This reagent combination also converts carboxylic acids to acyl chlorides (see Section 3.4.1). The mechanistic basis for the special effectiveness of benzotriazole has not yet been determined, but it seems likely that nucleophilic catalysis is involved. Sulfinyl ester intermediates may be involved, because Z-2-butene-l,4-diol gives a cyclic sulfite ester with one equivalent of reagent but the dichloride with two equivalents. 

As already shown, it is technically possible to incorporate additive functional groups within the structure of a polymer itself, thus dispensing with easily extractable small-molecular additives. However, the various attempts of incorporation of additive functionalities into the polymer chain, by copolymerisation or free radical initiated grafting, have not yet led to widespread practical use, mainly for economical reasons. Many macromolecular stabiliser-functionalised systems and reactive stabiliser-functionalised monomers have been described (cf. ref. [576]). Examples are bound-in chromophores, e.g. the benzotriazole moiety incorporated into polymers [577,578], but also copolymerisation with special monomers containing an inhibitor structural unit, leading to the incorporation of the antioxidant into the polymer chain. Copolymers of styrene and benzophenone-type UV stabilisers have been described [579]. Chemical combination of an antioxidant with the polymer leads to a high degree of resistance to (oil) extraction. 

Adamantylation of benzotriazole represents a special case because direct substitution in adamantanyl halides by an Sn2 mechanism is impossible, and an SnI mechanism is improbable. In this case, reactive cation 91 is generated by oxidative cleavage of the C-I bond in 1-iodoadamantane 90. Benzotriazole added to the reaction mixture binds cations 91 to afford a mixture of benzotriazol-l-yl 92 and -2-yl 93 derivatives in a ratio of 26 74 and the total yield of 67% (Scheme 5) <2001RJ01762>. 

Some data on the application of nitroazole derivatives have been mentioned in reviews and monographs on the chemistry of nitroazoles [1], pyrazoles [2], furox-ans [3], benzimidazole [4], and benzotriazole [5, 6], etc. Special monographs and reviews have been devoted to biological and clinical application of different nitroimidazoles [7-23] and chemotherapy of metronidazole [24], Therefore, it is not given much attention to metronidazole here. 

Although the parent compound 1,2,3-triazole has not been studied, the crystal structure of benzotriazole (18) has been determined (74AX(B)1490). Benzotriazole crystallizes in the space group P2i. In association with its remarkable anticorrosion activity (Section 4.11.6.4.2) benzotriazole and its conjugate base form stable transition metal complexes whose crystal structures have, in part, been studied. Some examples are presented in Figures 5-7, with special regard to the molecular dimensions of the benzotriazole moiety. 

Some special examples follow. Recently phase-transfer-catalyzed alkylation has been carried out on benzotriazole in benzene/aqueous NaOH in the presence of [PhCH2NEt3]" Cr. Both possible derivatives (137) and (138) were obtained (78MI41101>. 

Numerous patents have appeared in the last few years which deal with 1,2,3-triazoles and benzotriazoles as part of optical brightening molecules. These consist in most cases of stilbene moieties with suitable heterocyclic chromophores attached , and as a consequence hundreds of brighteners are available today on the world market. Special applications are whitening of fibers [e.g. poly(ethyleneterephthalate), cellulose acetate and poly(acrylonitrile)], lacquers and plastics. Several examples of the structural types involved are shown in Scheme 13. 

This section also includes the guanidinium salts formed with benzotriazole-based moieties such as HOBt and HOAt. In addition, haloformamidinium salts, which are the usual intermediates for the synthesis of uronium/guanidinium compounds and have occasionally themselves been employed in special coupling reactions, will be included in this section. 

DuPont [63] claimed a process for stabilisation of dyed poly(trimethylene terephthalate) fibres by adding a speciality benzotriazole in the dye bath (Cibafast USM Ciba). The structure of this additive was not revealed, but it most probably features extra substituents in the form of sulfonic acid(s) or derivatives thereof, which would allow the additive to be dispersed or dissolved in the aqueous dye bath. 

Ciba Speciality Chemicals have patented molecules which contain benzotriazole and hindered amine functional groups [60], e.g., 1(2-hydroxy-2-methylpropoxy-2,2,6,6-tetramethylpiperidin-4-yl)-3-(5-chlorobenzotriazol-2-yl)-5-tbutyl-4-hydroxycinnamate, and have also claimed their efficiency in PET, particularly in the form of fibres. 

Key A, benzophcnone UV absorbers B. benzotriazole UV absorbers C. HAl,Ss I). special stabilizer blends. 

A special case of aminals is the one derived from benzotriazole. These Ar-(a-aminoalkyl)triazoles 27 are readily prepared by condensation of an amine, aldehyde, and, in this case, benzotriazole. The derivatives 27 can be regarded as masked imines/iminium ions and can react with the appropriate nucleophiles in a Mannich sense. Thus treating the enolate of cyclohexanone (28) with a diverse array of triazoles (27) was able to give rise to the corresponding Mannich bases 29. 

In the first group, primary amines are reacted with carbonyl insertion compounds such as phosgene [727, 729], and sometimes phosgene substitutes such as triphosgene [507], various carbonates [503, 730, 731], bis(4-nitrophenyl)carbonate [503], di-ferf-butyl dicarbonate [664], S,S-dimethyl thiocarbonate [577], and N,N -carbonyldiimidazole [732], l,l-carbonylbis(benzotriazole) [728], and trihaloacetyl chlorides. Most of these compounds have been utilized as safer reagents that can be stored and handled without special precautions. 

Special phosphonium salts, such as (benzotriazol-l-yl-oxy-)tris(dimethylamino)-phosphonium and (benzotriazol-l-yl-oxy-)tris(pyrrolidino)phosphonium salts with hexafluorophosphate counter anion (Fig. 10) have been introduced as coupling reagents in the synthesis of four model peptide sequences. ... 

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],... 

Alkali metal (K, Na) [ CJcyanides have been extensively employed in the formation of alkyl [ CJnitriles via nucleophilic displacement of leaving groups such as primary halides, sulfonates and trialkylammonium salts in examples too numerous to mention. In special cases (e.g., 1) other leaving groups have been used, such as benzotriazol-l-yl. The most important considerations in the choice of leaving group are often the ease of substrate preparation and the compatibility of the displacement reaction with substrate ancillary functional groups. 

Mineral oils are mainly used as base oils. Ester oils (- lubricants) and fatty oils are also used as base or additive. Anionic and nonionic -> surfactants act as emulsifiers. Corrosion inhibitors are amine salts, sulfonates and benzotriazol. -i-Metallic soaps and - fatty alcohols impart antifoaming. For special purposes, many of the additives for - lubricants are used. There are three types of cutting fluids ... 

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