Imidazole-1-sulfonyl azide

Besides short ELPS, longer ELPs have also been conjugated to synthetic polymers. In one approach, Cu(I)-catalyzed azide-alkyne cycloaddition click chemistry was applied. For this purpose, ELPs were functionalized with azides or alkynes via incorporation of azidohomoalanine and homopropargyl glycine, respectively, using residue-specific replacement of methionine in ELP via bacterial expression [133]. More recently, an alternative way to site-selectively introduce azides into ELPs was developed. Here, an aqueous diazotransfer reaction was performed directly onto ELP[V5L2G3-90] using imidazole-1-sulfonyl azide [134]. 

Recently the use of imidazole-1-sulfonyl azide hydrochloride (185) as a diazo transfer reagent has been reported (Scheme 3.25). This compound is a crystalline, shelf-stable... 

Scheme 3.25 Aikyi azides via the diazo transfer reaction using imidazole-1-sulfonyl azide hydrochloride ...

After its discovery in 2002, the copper-catalysed azide-allg ne dipolar cycloaddition (CuAAC) click reaction has found widespread application in glycoscience due to its broad tolerance of functional groups, offering high specificity and yield. It has found application in glycoproteins synthesis as well, for instance, in the transformation of the amine sidechain of lysine into an azide by treatment with imidazole-1-sulfonyl azide for subsequent CuAAC modification. Such methodology... 

Aryl azides (such as 13) can be easily prepared from their corresponding amines (12) in one or two steps. Three examples are given in Scheme 2a. The most common method is the diazotization of the amine with sodium nitrite under acidic conditions (giving diazonium species 14), followed by addition of sodium azide in an aqueous medium (route i in Scheme 2a) [44], In 2003, the synthetic method was improved by application of triflyl azide (TfN3), which allowed a one-step conversion and gave improved yields (route ii in Scheme 2a) [45]. Recently, the development of sulfonyl azides 15 (with R = imidazole [46] or R = benzotriazole [47]) was reported these proved to be more stable reagents and allowed a conversion under mild conditions (route iii in Scheme 2a). 

Scheme 2 Preparation and examples of aryl azides, (a) Three possible routes for the conversion of an aryl amine into its aryl azide (i) via diazotization [44], (ii) by the use of triflyl azide [45], and (iii) with sulfonyl azides 15 (R = imidazole [46] or R = benzotriazole [55]). (b) Examples of substituted aryl azides...

Scheme 7.12 One-pot two-step synthesis which converts sulfonyl azides, terminal alkynes, and nitriles into imidazoles. The only byproduct of the reaction is a molecule of dinitrogen.

Wu and coworkers developed a Cu(I)-catalyzed three-component reaction of 2-(2-ethynylphenyl)oxiranes 111, sulfonyl azides 112, and ethyl a-isocyanoacetate (113) to afford 3 5 -dihydro-l//-spiro[benzo[d]oxepme-2,4 -imidazoles] 114 as a single diastereomer (Scheme 4.24) [44]. The reaction was initiated by a Cu(I)-catalyzed [3+2] cycloaddition between azide and alkyne to generate the intermediate 115. Subsequent release of nitrogen would provide the reactive ketenimine species 116. An intramolecular nucleophilic attack of epoxide to the ketenimine afforded the intermediate 117, which underwent fragmentation to provide 118. Finally, a [3+2] cycloaddition of 118 with a-isocyanoacetate 113 afforded the observed product 114. 

Tetrasubstituted imidazoles have been prepared from propargyl amines, sulfonyl azides, and terminal alkynes A-sulfonyl ketenimine and aminoallene are reported to be the key intermediates for the two-step one-pot transformation (Scheme 183). " ... 

Attempted displacement of the 2-O-imidazole-1 -sulfonyl ester of methyl 3,4,6-tri-O-rhethyl 3-D-galactopyranoside with azide ion led to the formation of the corresponding 2,5-arihydro sugar [86], as illustrated in Scheme 17. The predominance of a ring-contraction... 

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