Reduction aromatic amides

Reduction of amides to aldehydes was accomplished mainly by complex hydrides. Not every amide is suitable for reduction to aldehyde. Good yields were obtained only with some tertiary amides and lithium aluminum hydride, lithium triethoxyaluminohydride or sodium bis 2-methoxyethoxy)aluminum hydride. The nature of the substituents on nitrogen plays a key role. Amides derived from aromatic amines such as JV-methylaniline [1103] and especially pyrrole, indole and carbazole were found most suitable for the preparation of aldehydes. By adding 0.25 mol of lithium aluminum hydride in ether to 1 mol of the amide in ethereal solution cooled to —10° to —15°, 37-60% yields of benzaldehyde were obtained from the benzoyl derivatives of the above heterocycles [1104] and 68% yield from N-methylbenzanilide [1103]. Similarly 4,4,4-trifluorobutanol was prepared in 83% yield by reduction of N-(4,4,4-trifluorobutanoyl)carbazole in ether at —10° [1105]. 

Sodium and sodium amalgam may be used for reduction of amides but the yields of amines are generally very low. Primary aromatic amides (benz-amides) were reduced at the carbonyl function with 3.3 equivalents of sodium in liquid ammonia and ethanol while in tert-butyl alcohol reduction took place in the aromatic ring giving 1,4-dihydrobenzamides [984. ... 

The a-hydroxyamino intermediates from reduction of aromatic amides in acetonitrile can be trapped in the presence of chlorotrimethylsUane and subsequent work-up yields the aromatic aldehyde in good yields. This reaction has been car-... 

A trichlorosilane/tertiary amine mixture has been shown to reduce the carbonyl moiety of aromatic amides to give ASMAs. This constitutes an alternative to the reductive silylation described in Section III.B.2.f.194 This work has been reviewed195 and extended to aliphatic amides to give RSMA. 

Biphenylcarboxylic acids 3.43.6.7 Intramolecular reductive alkylation 3.43.7 Aromatic Carboxylic Esters 3.4.3.8 Aromatic Amides 3.43.9 Aromatic Ketones... 

Aromatic amide oximes are reduced in acid solution similarly to other reducible derivatives of hydroxylamine [1,99] the first step is a reductive loss of oxygen. The reduction of benzamide oxime thus yields benzamidine [1] ... 

Sonn-Miiller method The reduction of an aromatic amide to an aldehyde, in which the intermediate HC1 salt of the imine is formed from the amide and PC15. This salt is then reduced to... 

Aromatic amides are also electroactive at mercury or lead cathodes in strongly acidic solutions and afford amines. The use of less acidic solutions [70] leads to the reductive scission of the amide C—N bond. 

The reduction-deoxygenation coupling of aromatic amides in the presence of stoichiometric amount of organosi-lanes is catalyzed by Cp2TiX2 (X = F, Me).1249-1251... 

The reagent reduces aromatic nitro compounds to the corresponding amines in about 80% yield.1 Ester, nitrile, ether, halide, or double bonds, if present, are not affected. Primary aliphatic nitro compounds are reduced to the corresponding nitrile in high yield. The reduction of amides gives only moderate yields of the corresponding amines.8... 

The carbonylation of aryl halides with alcohols and amines catalysed by palladium complexes with triphenylphosphine ligand is the convergent and direct route to the synthesis of aromatic esters as well as aromatic amides. Even though these palladium complexes are widely employed as the best catalytic system, those catalysts are difficult to separate and reuse for the reaction without further processing. The major drawbacks are oxidation of triphenylphosphine to phosphine oxide, reduction of palladium complex to metal and termination of the catalytic cycle. The phosphine-free, thermally stable and air resistant catalyst (1) containing a carbon-palladium covalent bond (Figure 12.3) has been found to be a highly selective and efficient catalyst for the carbonylation of aryl iodides.[1]... 

Reductions. Aromatic carboxylic acids, esters, and amides are reduced to ArCH20H and nitriles to ArCH2NH2 by the Sml2-H20 system. Pyridine derivatives are completely reduced to afford piperidines in aqueous THF. With MeOH as a proton source the labile 2-aminonitroalkanes are converted to the diamines." ... 

Imines are reduced by triethylsilane to their amines when the proper Ir orNi catalysts areemployed. Non-metal-mediated reductions of C=N groups by EtsSiH are also possible. Among these, the trifluorosulfonic acid promoted reductive amidation of aliphatic and aromatic aldehydes with EtsSiH is an excellent way to mono (V-alkylate aliphatic and aromatic amides, thioamides, carbamates, and ureas (eq 26). It is also worth noting that trifluorosulfonic acid/EtsSiH reduces acyl- and tosylhydrazones to hydrazines and 2-aminopyrimidines to 2-amino-dihydro-or 2-aminotetrahydropyrimidines (eq 27). ... 

Rains, R. K. Fields, D. L. Triplett, R. D. Process for preparing aromatic azo and hydrazo compounds, aromatic amides and aromatic amines via aromatic nucleophilic suhstitution or oxidative coupling, and either aminolysis, hydrolysis, reduction and/or reductive alkylation. U.S. Pat. Appl. Puhl. US 2004039181, 2004 Chem. Abstr. 2004,140, 217375. 

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