0-amino benzaldehyde cyanohydrin

It may be prepared by any one of the following three methods Method-I From o-Amino benzaldehyde cyanohydrin... 

Second, a nitrile is reduced to a primary amine by hydrogen in the presence of nickel or another transition metal catalyst (Section 18.10C). Catalytic reduction of benzaldehyde cyanohydrin, for example, gives 2-amino-l-phenylethanol. 

A fascinating variant of the enzymatic cyanohydrin formation consists in the use of nitroalkanes (as nonnatural nucleophiles) instead of cyanide (Scheme 2.209) [1568,1569]. Overall, this constitutes a biocatalytic equivalent to the Henry-reaction producing vicinal nitro-alcohols, which are valuable precursors for amino alcohols. Using (5)-HNL, the asymmetric addition of nitromethane to benzaldehyde gave the nitroalcohol in 92% e.e., while for p-nitrobenzaldehyde the stereoselectivity dropped sharply. With nitroethane, two stereocenters are created Whereas the stereoselectivity for the alcoholic center was high (e.e. 95%), the recognition for the adjacent center bearing the nitro moiety was modest and other (dia)stereomers were formed in up to 8%. 

The enantiomerically pure amino acids also can be produced through a similar synthetic pathway catalyzed by enzymes. For example, reaction of hydrogen cyanide with benzaldehyde catalyzed by either (R)- or (S)-oxynitrilase enzyme yields the enantiomeric cyanohydrins (R)- or (S)-mandelonitrile. Alternatively, by adding carbon dioxide and hydrogen cyanide and ammonia as feedstocks, aldehydes can be converted to hydantoins (4-alkylimidazolidine-2,5-diones), which can be then hydrolyzed with either D- or L- hydan-toinases to produce D- or L-a-amino acids, respectively. 

The reduction of acylcyanide using neat (f )-Alpine-Borane affords the corresponding (i )-P-amino alcohols [4cj. The reduction of acylcyanide and subsequent workup is not a straightforward process. The reaction of benzoylcyanide with neat Alpine-Borane (1.5 equiv) is complete within 2 h. The cyanohydrin-9-BBN adduct builds up to maximum, and then decreases with the appearance of a 9-BBN-benzyl alcohol adduct. Apparently, the 9-BBN-cyanohydrin adduct undergoes an elimination reaction to give benzaldehyde, which then undergoes reduction. The results indicate that the desired bimolecular reduction process can compete with the elimination reaction. 

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