Oxidative Azide

This new assay technique was developed independently by American and Australian workers who first established the connection between nitrogenase and hydrogenase, and showed the former could reduce a number of substrates other than nitrogen, for example nitrous oxide, azide, cyanide and, most usefully, acetylene. The latter is reduced to ethylene and this forms the basis of the acetylene reduction test. The material to be examined is briefly gassed with acetylene and the ethylene formed measured by gas chromatography. While this technique was being refined,... 

X-ray structures of 2.8-A resolution of bovine heart cytochrome c oxidase with the metals in the fully oxidized state were reported in 1995 (Tsukihara et al., 1995). The X-ray structure of cytochrome c oxidase from Paracoccus denitrificans in the fuUy oxidized azide-bound state at 2.8-A resolution was also published in the same week (Iwata et al., 1995). The structure and location of the metal sites of the two enzymes are astonishingly similar at that resolution. Later, the resolution of the bovine enzyme structure was improved to 2.3A (Yoshikawa et al., 1998). However, resolution of the Paracoccus enzyme has been improved to 2.7-A resolution (Ostermeier et al., 1997). Recently another bacterial ba3-type oxidase at 2.3-A resolution (Soulimane et al., 2000) and Escherichia coli quinol oxidase at 3.5-A resolution were reported (Abramson et al., 2000). X-ray structures of the protein and its redox-active metal sites are discussed in terms of the bovine enzyme below. 

Peroxynitrite ion. This ion, produced by oxidizing azide solutions by O3 or NH2CI by O2, apparently exists in methanol solutions for weeks. Its presence has been demonstrated by its u.v. absorption spectrum, but no solid salts have been obtained. The structure (0=N—0—0) has been suggested. ... 

Lead azide, Pb(N3)2, can be analysed by voltammetry, oxidizing azide ions at a carbon paste electrode and reducing lead ions at a dropping mercury electrode at pH 4.6 in an acetate buffer solution. Lead azide is poorly soluble in a pure aqueous solution, but can be dissolved when acetate ions are present. In Fig.l7 a differential pulse voltammogram for the determination of azide at a carbon paste electrode is shown. Some results from the analysis of lead azide are given in Table 7. 

In 2010, Studer et al. reported A -heterocyclic carbene catalyzed oxidative amidations of various aldehydes to the corresponding acyl azides by using the readily available organic oxidant [43]. Acyl azides can readily be converted via thermal Curtius rearrangement to carbamoyl azides as shown for the transformation of benzaldehyde to phenyl carbamoylazide (Scheme 5.7), when r-BuOH was further added to the crude reaction mixture, which was then heated for 1 h to reflux. Therefore, a mild NHC-catalyzed oxidative azidation of aromatic aldehydes to form the corresponding acyl azides which can be rearranged to carbomoylazides in the same pot. 

Scheme 5.7 NHC-catalyzed oxidative azidation of aromatic aldehydes to carbomoylazides in one pot...

Employing A-heterocyclic carbine (NHC) catalysis, in 2010, Sarkar and Studer presented a novel and efficient oxidative azidation of aromatic aldehydes by using 3,3 5,5 -tetra-tert-butyldiphenoquinone as the oxidant (Scheme 6.23) [77]. Reaction works with a low catalyst loading under mild conditions and the acyl azides are obtained in good yields. They further showed that the acyl azides can be rearranged to carbamoyl azides in the same pot. 

Scheme 6.31 Decarboxylative oxidative azidation of malonic acid monoestos...

Kita Y, Tohma H, Inagaki M, Hatanaka K, Yakura T (1991) A novel oxidative azidation of aromatic compounds with hypervalent iodine reagent, phenyliodine(III) bis(trifluoroacetate) (PIFA) and trimethylsilyl azide. Tetrahedron Lett 32(34) 4321 324... 

Ren R, Zhao H, Huan L, Zhu C (2015) Manganese-catalyzed oxidative azidation of cyclobutanols regiospecific synthesis of alkyl azides by C-C bond cleavage. Angew Chem IntEd 127(43) 12883-12887... 

Scheme 7.49 Synthesis of quinoxaline derivatives via tandem oxidative azidation/cyclization...

Ma H, Li D, Yu W (2016) Synthesis of quinoxaline derivatives via tandem oxidative azidation/cyclization reaction of N-arylenamines. Org Lett 18(4) 868-871... 

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