Cyano 4-nitrobenzyl

Potassium and sodium borohydride show greater selectivity in action than lithium aluminium hydride thus ketones or aldehydes may be reduced to alcohols whilst the cyano, nitro, amido and carbalkoxy groups remain unaffected. Furthermore, the reagent may be used in aqueous or aqueous-alcoholic solution. One simple application of its use will be described, viz., the reduction of m-nitrobenzaldehyde to m-nitrobenzyl alcohol ... 

The final step can involve introduction of the amino group or of the carbonyl group. o-Nitrobenzyl aldehydes and ketones are useful intermediates which undergo cyclization and aromatization upon reduction. The carbonyl group can also be introduced by oxidation of alcohols or alkenes or by ozonolysis. There are also examples of preparing indoles from o-aminophcnyl-acetonitriles by partial reduction of the cyano group. 

To avoid any loss of benzyl ester protection during acidolytic removal of the benzyloxy-carbonyl and ferf-butoxycarbonyl groups, electron-withdrawing substituents were used to destabilize the intermediate benzyl cation and thus to increase the acid stability. In addition to the very useful 4-nitrobenzyl esters (vide infra), the picolyl ester (see Section 2.2.1.2.2.3) as well as halo-P l or cyano-P°°l substituted benzyl esters have been reported, the latter being rarely used for a-carboxy protection. Conversely, an increase in sensitivity toward acids can be achieved by introduction of electron-releasing substituents, such as methoxy or methyl groups. Addition of scavengers to quench intermediate carbocations and to prevent electrophilic substitutions at sensitive amino acid side chains is beneficial in the deprotection of such esters. 

C7H5N2CI 2-chloro 3-cyano-6-methylpyridine 35747-58-1 25.00 1.3106 2 10244 C7H6CIN03 4-chloro-3-nitrobenzyl alcohol 55912-20-4 i 25.00 1.4048 2... 

A similar reaction is found in the formation of 5-amino-l-cyano-2,4-dimethyl-3.106-dihydrobenzo[c][2,7]naphthyridine by reduction of 3,5-dicyano-2,6-dimethyl-4-(2-nitro-phenyl)-l,4-dihydropyridine [87] and tetrahydroquino[2,l-c]benzodiazepines from 2-cyano-l-(2-nitrobenzyl)-l,2,3,4-tetrahydroquinoline [88], When the hydroxylamino group has a choice between a nitrile or an ester group, as in 3-ethoxycarbonyl-5-cyano-2,6-dimethyl-4-(2-nitrophenyl)-1,4-dihydropyridine, it condenses with the nitrile in acidic solution and with the ester in basic media [89]. 

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