Terminal azides

Figure 17.21 An azido-farnesyl diphosphate derivative can be added to cells to obtain farnesylated proteins containing terminal azide groups that can be targeted in a Staudinger ligation reaction. Biotinylation of these post-translationally modified proteins can be done in vivo using a biotin-phosphine derivative.

A further interesting X-ray structural study has been that of (AsPh4)2-[Pd2(N3)6] (66). This reveals similar asymmetry in the two N—N bond lengths for the bridging (1.239 and 1.142 A) and terminal (1.205 and 1.139 A) azide groups. Such structural equivalence indicates that there is no appreciable change in electronic character when a terminal azide co-ordinates to a second Pd via a normally unshared electron pair on the trigonal N atom (see Table... 

Frankel, M.B., and Flanagan, J.E. (1981) Energetic hydroxy terminated azide polymer. US Patent 4,268,450. 

Fig. 52. Scanning with a platinum coated SFM tip over a SAM surface containing terminal azide groups in the presence of H2 leads to the reduction of azide groups to primary amino groups. Derivatization of the resulting amine surface with aldehyde-modified latex beads results in specific labelling of the reduced areas. Reproduced from [469]...

One of the earliest Schiff base macrocycles to exhibit a haemocyanine-like structure was the copper(II) perchlorate complex of 5.5 which binds readily to azide or hydroxide.8 The azide complex exhibits two square pyramidal copper binding domains with the basal plane occupied by one pyridyl nitrogen atom and two imine functionalities as well as a terminal azide ligand. The apices of the two pyramidal coordination polyhedra are linked by a single bridging azide anion. Continuing the biomimetic theme, manganese (II) cascade complexes of the unsymmetrical 5.6 have... 

The thermal decomposition of terminal vinyl azides was originally believed to give only nitriles or, in some cases, indoles. The presence of 3-monosubstituted 1-azirines, however, has been inferred in the photolytic decomposition of some terminal azides.22,29 30 The nitrile is thought to arise in a similar manner to the ketenimine by an analogous Curtius-type rearrangement. The ketenimine (53) derived from terminal azides is unstable and rearranges to the nitrile (54). 

In order to prepare SWNT-Au nanocrystal composites, SWNTs were functionalized by amidobutane (with a terminal azide group) as follows. Acid-treated SWNTS were reacted with thionyl chloride, followed by reaction with 4-azidobutylamine. These SWNTs were reacted with hexy-nethiol-capped Au nanocrystals. 

At present some preliminary evidence has been obtained which suggests that sapphyrins can bind anions other than fluoride. In fact, an X-ray diffraction study shows that NJ binds to the monoprotonated form of sapphyrin [157]. Specifically, as shown in Fig. 29, the monoprotonated sapphyrin, H4Sap Nj, does not complex azide anion in an in-plane fashion but in an end-on manner, with the terminal azide nitrogen atom being 1.13 A above the sapphyrin plane [157]. Nonetheless, this atom is still vsdthin typical hydrogen bonding distance (2.8 to 3,0 A) of at least four of the five pyrrolic nitrogens [59, 173-176]. 

Nucleophilic attack on the terminal azide nitrogen by ylides... 

A better method for the preparation of the terminal isomers has resulted from the observations that bromine azide, unlike iodine azide, may be induced to add to olefins by a free-radical mechanism . Thus, when styrene was subjected to the addition of bromine azide in pentane a quantitative yield of the precursor 23 for the terminal azide was obtained, while reaction in a more polar solvent gave a very high yield of the opposite regioisomer 24. 

The recently reported results of Isomura and co-workers suggest that azirines are generally formed on p Tolysis of terminal azides, but that 2-unsubstituted azirines are too unstable to survive most pyrolysis... 

Figure 10 Carbohydrate microplate arrays prepared by the noncovalent immobilization of azide-derivatized carbohydrates to microtiter plates via a 1,3-dipolar cycloaddition reaction between alkynes and azides. Carbohydrates displaying terminal azides can be captnred on microtiter plate surfaces through a terminal alkyne attached to a long, ahphatic tether and screened directly on the microtiter plate surface.

Click ligation Protein with a C-terminal azide Non-natural bond Rabl, Rab7... 

In a similar convergent strategy, the Monteiro group have demonstrated the preparation of well-defined, three-miktoarm star polymers using a combination of ATRP and CuAAC [108]. As discussed previously, polymers prepared via ATRP can be easily transformed by a nucleophihc displacement of the terminal halides with sodium azide to yield cUck -functional materials. In this way, PS, poly(t-butyl acrylate) (PtBA), and poly(methyl acrylate) (PMA), all of which bore a terminal azide... 

Santner T, Haiti M, Bister K, Micura R (2014) Efficient access to 3 -terminal azide-modified RNA for inverse click-labeling patterns. Bioconjug Chem 25(1) 188-195. doi 10.1021/bc400513z... 

Scheme P12.4.1 Synthesis of macrocyclic polystyrene by terminal azidation and CuAAC reaction on linear polystyrene prepared by ATRP (Tsarevsky, et al., 2005 Laurent and Grayson, 2006.)...

Derivatives of Z-2-butene-l,4-diol have been used in terminal CM reactions, most notably esters thereof that served as ATRP initiator sites [39, 38]. The same symmetrical olefin (Figure 3.6, bottom) was used by Gozgen et al. [40] to prepare polymeric terminal azides for subsequent polymer analogous click reactions ... 

Mention should also be made of the modular synthesis of block copolymers by the so-called cKck chemistry, designed for instance by Opsteen and van Hest [68]. These authors prepared a large variety of block copolymers via a high yield 1,3-dipolar cycloaddition coupling reaction of terminal azide and alkyne precursor blocks as illustrated in the following scheme ... 

Opsteen, J.A. and van Hest, J.C.M. (2005) Modular synthesis of block copolymers via cycloaddition of terminal azide and alkyne functionalized polymers. Chem. Commun., 1, 57-59. 

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