Azides to amines

Degradation of acid hydrazides or acyl azides to amine or amine derivatives. 

Aqueous solutions of vanadous chloride (vanadium dichloride) are prepared by reduction of vanadium pentoxide with amalgamated zinc in hydrochloric acid [213], Reductions are carried out in solution in tetrahydrofuran at room temperature or under reflux. Vanadiiun dichloride reduces a-halo ketones to ketones [214], a-diketones to acyloins [215], quinones to hydroquinones [215], sulfoxides to sulfides [216] and azides to amines [217] (Procedure 40, p. 215). 

In very reactive halogen derivatives such as a-bromo ketones [234] and a-bromothiophene [235] the halogens are replaced by hydrogen with hydrogen bromide in acetic acid provided phenol is added to react with the evolved bromine and to affect favorably the equilibrium of the reversible reaction. Hydrogen bromide in acetic acid also reduces azides to amines [232],... 

RN3- RNH2 The reduction of azides to amines normally proceeds in poor yield, but can proceed in 79-92% yield if carried out with NaBH4 in toluene-water in the presence of hexadecyltributylphosphonium bromide as phase-transfer catalyst. 

Exposure of sulfolane 261 to sodium azide and mesylation regioselectively afforded mesylate 262, which was transformed into aziridine 263 by a three-step sequence involving azide to amine Staudinger reduction, acetylation, and ring closure. The trans 1,2-diamino derivative 264 was quickly obtained from 263 by azide opening of the aziridine ring, followed by reduction. 

Warrier, M., M.K.F. Lo, H. Monbouquette and M.A. Garcia-Garibay (2004). Photocatalytic reduction of aromatic azides to amines using CdS and CdSe nanoparticles. Photochemical and Photobiological Sciences, 3(9), 859-863. 

The conversion of azides to amines is discussed elsewhere (method... 

The conversion of hydrazides and azides to amines has been described in Section VIII. 1A(6). 

Smooth conversion of azides to amines was achieved by using hydrogen bromide in acetic acid solution . The reduction is, when possible, accompanied by bromination by the liberated bromine. The bromination can be prevented by addition of a bromine acceptor. 2-Azido-5-nitrobiphenyl (23) thus yielded 2-amino-3-bromo-5-nitrobiphenyl (24), but in the presence of phenol the product was 2-amino-5-nitrobiphenyl (25) . The method has also been used with amino acids, acetone serving as a bromine acceptor . 

Amines from azides. Reduction of various azides to amines... 

Reduction of azides to amines. Reduction of an azide to the corresponding amine by the conventional method of hydrogenation is impractical if the molecule contains sulfur. In this case an alternative procedure is reduction with sodium borohydride in isopropanol, provided no other easily reduced group is present. This procedure can be used with acid-sensitive compounds. 

The Staudinger reaction is a mild method for the conversion of azides to amines by treating the azide with triphenylphosphine in the presence of water. The water is necessary, because the intermediate iminophosphrane is hydrolyzed to form the amine and triphenylphosphine oxide. Reviews (a) Gololobov, Y. G. Kasukhin, L. E Tetrahedron 1992, 48, 1353-1406. (b) Gololobov, Y. G. Zinnurova. 1. N. Kasukhin, L. E Tetrahedron 1981, 37,437 72. 

In neutral media, they leave carbonyl derivatives intact but reduce tosylhydrazones to the corresponding hydrocarbons under reflux of CHCI3 (Section 3.3.4). This reduction is compatible with a-enone, epoxide, or lactone groups present in the molecule [GL3]. In cold acetone, these reagents reduce acid chlorides to aldehydes [FHl] (Section 3.2.7). In the presence of Lewis acids or gaseous HCl in CHjClj, they reduce aldehydes and ketones. The selective reduction of aldehydes in the presence of ketones can also be realized (Section 3.2.1). These reagents also reduce aromatic azides to amines (Section 5.2). 

The reduction of azides to amines with NaBH4-Ni(OAc)2 (Section 5.2) ... 

CH2CI2, DMAP, rt, 87% yield or pyridine). It is cleaved by reduction of the azide with BU3P or MePPh2 (THF, H20,76-96% yield) which causes facile intramolecular amide formation with release of the protected alcohol. Other conditions that reduce azides to amines such as hydrogenation (NH4HCO2, Pd-C, MeOH, rt) or NaBUi reduction will cleave this ester (86-98% yield). ... 

The most common reduction performed on the solid phase is the reductive amination. The reaction has been performed with either resin-bound amine or aldehyde. Reduction of a number of other functional groups has also been applied to the solid phase, usually to generate handles for further diversification, e.g. nitro to amine, azide to amine. 

Whilst conjugated en- and dien-ones are unaffected by chromium(ii) chloride, conjugated enediones are reduced to the saturated diketones.Chromium(ii) chloride is also an efficient reagent for the reduction of azides to amines. 

Figure 15-50. Reduction of azide to amine by bakers yeast1286, 28 l.

Among reactions of BSD, conversion of azides to amines, 66, deserves special attention (50, 81, 82) [Eq. (114)]. Below 0°C, BSD reacts only with... 

Fu and co-workers have recently used tin catalysts to reduce thionocarbonates in which the turnover step is the reaction of BusSnOPh with PMHS (cf. Eq. 10) [38]. The same group has established Bu3SnH-catalyzed reductions of nitroalkanes to alkanes and azides to amines using PhSiH3 as the reagent for the regeneration of the tin catalyst [39, 40]. 

Tin(IV) bis(l,2-benzenedithiolate) has been used to mediate the reduction of azides to amines. ... 

Reduction of azides to amines. The reduction of azides to amines is usually carried out by catalytic hydrogenation or with lithium aluminum hydride. Neither method is selective. Corey et al. have used Lindlar catalyst for selective reduction of azides in the presence of carbonyl groups, double bonds, and benzyl ether groups. An acetylenic function is also reduced to the cti-olefin. Representative amines obtained in this way, with the yields, are formulated. 

Metal Hydrides. A number of patents and publications have appeared describing the use of lithium aluminum hydride in the reduction of nitro compounds, nitriles, amides, oximes, and azides to amines. Moderate to high yields have been obtained. This process is useful in the selective reduction of compounds sensitive to catalytic hydrogenation, but is quite costly. 

RN3 —3 RNH2. The dichloroborane complex is a highly selective reducing agent tor converting azides to amines (8 examples, 75-95%). 

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