Nitro nitriles, reduction

Protiodenitration. Simple nitroalkanes are not reduced by 1, but a-nitro nitriles, esters, and ketones are selectively reduced by 1 under irradiation, with selective replacement of NO by H. The reduction occurs via an electron-transfer chain mechanism. Example ... 

Reduction of azides. Alkyi and aryi azides are reduced to primary amines by the combination of 1,3-propanedithiol and triethylamine (equation 1). The method is highly selective, and does not affect double or triple bonds, nitro, nitrile, carboxylic acid, amide, and ester groups. ... 

This reagent also reduces nitro, nitrile, and amide derivatives to amines, and carboxylic acids and anhydrides to alcohols. The yields of these reductions arc nearly quantitative. Esters and halobenzene derivatives are not reduced. 

If other active groups are present y or S to the reducible nitro group, hydrogenation can result in formation of nitrogen heterocyclic products. Several such cyclizations provide an entry to indoles, such as reductive cyclizations of dinitrostyrene 1 [equation (a)], of o-nitrobenzyl ketone 2 [equation (b)], and of nitro nitrile 3 [equation (c)] , all of them carried out on palladium-on-carbon. 

Reductive cyclization of a nitro-nitrile yields a fused pyrrole ring. 

Electrocatalytic hydrogenation of several nitriles was investigated using Ra-Ni or Pd/C powders placed onto a Ni plate and Table 10 summarizes some of these results. On Ra-Ni, the reduction occurred more efficiently than on Pd/C. With the latter, higher selectivity for nitro group reduction in the presence of cyano group was achieved (entries 5-6). 

Hantzsch ester (2, R = Et) and an organocatalyst -benzyl isothiouronium chloride, prepared from thiourea, catalysed the reductive amination of aromatic, aliphatic, heterocyclic, and cyclic aldehydes to amines in high yields. Aliphatic aldehydes reacted with difficulty and required a higher temperature. Nitro, nitrile, and carbonyl moieties were not reduced. ... 

Amine precursors, such as nitro, nitrile, and azido compounds, which can be converted to amines under the hydrogenation reaction conditions, can also be used in the reductive alkylation reaction (Scheme 26). 

Carbonyl Compounds Multiple Bond Reduction Nitrile Group Nitro Compounds Reductive Amination Wolff-Kishner Reduction... 

The imides, primaiy and secondary nitro compounds, oximes and sulphon amides of Solubility Group III are weakly acidic nitrogen compounds they cannot be titrated satisfactorily with a standard alkaU nor do they exhibit the reactions characteristic of phenols. The neutral nitrogen compounds of Solubility Group VII include tertiary nitro compounds amides (simple and substituted) derivatives of aldehydes and ketones (hydrazones, semlcarb-azones, ete.) nitriles nitroso, azo, hydrazo and other Intermediate reduction products of aromatic nitro compounds. All the above nitrogen compounds, and also the sulphonamides of Solubility Group VII, respond, with few exceptions, to the same classification reactions (reduction and hydrolysis) and hence will be considered together. 

Analysis There are two general ones based on reduction of nitrile or nitro compound (a) nitrile route... 

Reduction of an azide a nitrile or a nitro compound furnishes a primary amine A method that provides access to primary secondary or tertiary amines is reduction of the carbonyl group of an amide by lithium aluminum hydride... 

The preparation of amines by the methods described m this section involves the prior synthesis and isolation of some reducible material that has a carbon-nitrogen bond an azide a nitrile a nitro substituted arene or an amide The following section describes a method that combines the two steps of carbon-nitrogen bond formation and reduction into a single operation Like the reduction of amides it offers the possibility of prepar mg primary secondary or tertiary amines by proper choice of starting materials... 

Electrolytic Reductions. Both nitro compounds and nitriles can be reduced electrochemically. One advantage of electrochemical reduction is the cleanness of the operation. Since there are a minimum of by-products, both waste disposal and purification of the product are greatiy simplified. However, unless very cheap electricity is available, these processes are generally too expensive to compete with the traditional chemical methods. 

AletalHydrides. Metal hydrides can sometimes be used to prepare amines by reduction of various functional groups, but they are seldom the preferred method. Most metal hydrides do not reduce nitro compounds at all (64), although aUphatic nitro compounds can be reduced to amines with lithium aluminum hydride. When aromatic amines are reduced with this reagent, a2o compounds are produced. Nitriles, on the other hand, can be reduced to amines with lithium aluminum hydride or sodium borohydride under certain conditions. Other functional groups which can be reduced to amines using metal hydrides include amides, oximes, isocyanates, isothiocyanates, and a2ides (64). 

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