Azido halides—

Photochemically produced small atoms (H, C, N, O, F), co-deposited with matrix-isolated substrates, led to a wide variety of unstable molecules and radicals. This synthetic route is very efficient if the substrate itself acts as a matrix material (O2, CO, CH4). Apart from these reactions, photo-induced decomposition and isomerization processes of matrix-isolated molecules can be studied by vibrational spectroscopy. Photoelimination of small, thermodynamically stable molecules (N2, CO2, CF4, HF,...) from a precursor is the most important photoprocess for generating unstable molecules in low-temperature matrices. Photochemical loss of dinitrogen from azido and diazo compounds is frequently observed in matrices. One example is that of azido halides (Milligan and Jacox, 1964). 

Vinyl azides are generally prepared from 2-azido halides by elimination, while vinylogous acid chlorides and similar systems may be treated with azide ions directly in an addition-elimination sequence (Scheme 34). With haloquinones smooth transformations into azidoquinones are also ob-served." " Thus all four chloro substituents of chloranil can be successively exchanged with azide ions (Scheme 34). 

Trimethylsilyl halides can also be used for analogous reactions with arenediazo-nium tetrafluoroborates, as shown by Keumi et al. (1989). These authors treated 2-fluorenediazonium tetrafluoroborate in A/,Af-dimethylformamide or -acetamide with trimethylsilylchloride, -bromide, or -iodide in the presence of an excess of N-chlorosuccinimide, Af-bromosuccinimide, or methyl iodide, respectively, at 60 °C (Cl, Br) or at room temperature (I). The yields of the 2-halofluorenes were good in addition fluorene, the product of hydro-de-diazoniation, was obtained, if the reaction was run in tetrahydrofuran/Af,7V-dimethylformamide mixtures. The mechanism of these reactions, as well as that of the corresponding azido-de-diazoniation, is uncertain (see also Secs. 10.2 and 10.7). 

The chemistry of the azido group The chemistry of the acyl halides The chemistry of the carbon-halogen bond (2 parts)... 

The Chemistry of the Azido Group The Chemistry of Acyl Halides... 

Azides 1253 obtained from propargyl halides or sulfonates 1252 undergo sigmatropic rearrangement to azidoal-lenes 1254, which subsequently undergo cyclization to triazafulvenes 1255. Under the reaction conditions, species 1255 react with another molecule of sodium azide to furnish triazoles 1256. Products 1256 are isolated in 65-97% yield (Scheme 209) <2005S1514>. 

Reaction of hydrazinoazines with nitric acid has also proved to be suitable route to form azido moieties to complement the nucleophilic exchange reaction of a halide for an azide. This approach has also been applied recently for the synthesis of fused tetrazoles, and these transformations are shown in Scheme 24. 

Paulsen and associates (58) synthesized mono- and di-D-galactopyranosyl derivatives of L-serine/L-threonine. Condensation of the 2-azido-2-deoxy-glycosyl halides 61 and 62 with the benzyl or tert-butyl esters of iV-benzyl-oxycarbonyl (Z)-protected L-serine, L-threonine, and L-leucyl-L-serine (63 -65) in the presence of silver carbonate, silver perchlorate, Drierite, and molecular sieves gave (59) the corresponding O-glycopeptides 67-69. The free glycopeptides were obtained after total deprotection. 

For a study of nitrophenylbenzotriazoles as explosives, the triazole ring conferring impact sensitivity, see [1]. Simpler nitro- and azido-triazoles also find explosive use. On heating to above 260°C, 1,2,3-triazole halides explode violently [2], Several examples of instability among this group of relatively high-nitrogen compounds may be found under the entries ... 

Azido-4-0-benzoyl-2,3 6 trideoxy-2-fluoro-D-r/Ao-hexopyranosyl halide... 

The iminophosphorane 177 available from methyl azido(phenylhydrazo-no)acetate by a Staudinger reaction represents an ideal starting material for the synthesis of l//-l,2,4-triazoles (180). Two synthetic routes are possible (Scheme 68). The first is the reaction of iminophosphoranes with halides via isolable A-acylphosphonium salts (178), and imidoyl chlorides (179), leading to triazoles. The other approach involves the less reactive anhy-... 

Alkyl azides are conveniently prepared from the reaction of alkali metal azides with an alkyl halide, tosylate, mesylate, nitrate ester or any other alkyl derivative containing a good leaving group. Reactions usually work well for primary and secondary alkyl substrates and are best conducted in polar aprotic solvents like DMF and DMSO. The synthesis and chemistry of azido compounds is the subject of a functional group series. ... 

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