Reduction of aromatic nitriles

Raney nickel alloy, reduction of aromatic nitriles to aldehydes, 51, 22 REACTION OF ARYL HALIDES WITH... 

Table 11 Yields of Aldehydes Prepared by the Stephen Reduction of Aromatic Nitriles ...

Prepared by the reaction of aluminum ethoxide with sodium hydride, it is a colorless, microcrystalline powder stable for several weeks in the absence of air and is used in ether or THF. A somewhat milder reducing agent than lithium aluminum hydride, it is recommended particularly for the reduction of aromatic nitriles to aldehydes C H,C N — C H.,CHO (95%). 

Hydrogenation of nitro compounds is rather straightforward, and palladium, platinum, and nickel catalysts have been used. Palladium is the most common catalyst for both aromatic and aliphatic nitro compounds. The poor results obtained for reduction of aromatic nitriles with hydride reagents (sec. 4.2.C.iii) make catalytic hydrogenation the preferred method. Reduction of 407 involved conversion of the aromatic nitrile moiety to the benzylamine derivative when palladium and a trace of platinum oxide was used. Hydrogenation using platinum oxide converts aromatic nitro compounds to aniline derivatives, even in the presence of other reducible groups. OS... 

The reduction of aromatic nitriles takes place without the occurrence of secondary reactions. This is illustrated in the formation of benzylamine from benzo-nitrile and of phenyl-ethylamine from benzyl-cyanide. 

Table 7.7 Selective reduction of aromatic nitriles in the presence of aliphatic nitriles with potas-...

Cyano-de-diazoniations of the Sandmeyer type have been used for the synthesis of aromatic nitriles for many decades (example Clarke and Reed, 1964), as cyanide ions are comparable to bromide and iodide in many respects. A homolytic cyano-de-diazo-niation that does not use metal ions as reductant or ligand transfer reagent was described by Petrillo et al. (1987). They showed that substituted diazosulfides (XC6H4 — N2 — SC6H5), either isolated or generated in situ from arenediazonium tetrafluoroborates and sodium benzenethiolate, react with tetrabutylammonium cyanide in dimethylsulfoxide under photon stimulation, leading to nitriles (XC6H4CN). The method worked well with eleven benzenediazonium ions substituted in the 3- or 4-position, and was also used for the synthesis of phthalo-, isophthalo-, and tere-... 

Rapid reduction of aromatic nitro compounds into amines has been described using sodium hypophosphite and FeSC>4-7H20. The reactions showed best results in terms of yields and purity, when the substrates were pre-absorbed on alumina and irradiated by microwaves under solvent-free conditions. The reaction is chemoselective and does not affect functional groups such as CN, OH, COOH, CONH2 or halogens. In addition, oximes were not reduced under the given reaction conditions, but were dehydrated to the corresponding nitriles instead (Scheme 4.32)57. 

This catalyst effects reduction of aromatic and tertiary nitriles to methyl groups in yields >85%. Aliphatic nitriles, however, mainly undergo hydrogenolysis.3... 

The great majority of applications of the Birch reduction have been centered on aromatic ethers, simple alkylbenzenes and bicyclic and polycyclic aromatic hydrocarbons. Over the past decade or so, however, there has been increasing attention given to other derivatives. The reductions of aromatic acids and amides have been placed on a systematic basis, while new procedures have been established for substrates which have until recently been regarded as unsuitable candidates for reduction, e.g. aromatic ketones and esters, and even nitriles,... 

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