By reduction of oximes

Derivatives of Aziridines Prepared by Reduction of Oximes with Lithium Aluminum Hydride... 

Scheme 3.12 Preparation of amino sugars by reduction of oximes.

Aldehydes and ketones may be converted into the corresponding primary amines by reduction of their oximes or hydrazones (p. 93). A method of more limited application, known as the Leuckart Reaction, consists of heating the carbonyl compound with ammonium formate, whereby the formyLamino derivative is formed, and can be readily hydrolysed by acids to the amine. Thus acetophenone gives the i-phenylethylformamide, which without isolation can be hydrolysed to i-phenylethylamine. 

By the reduction of oximes with sodium and absolute ethyl alcohol, for example ... 

Analysis The branchad chain can only be made by reduction of an oxime so we must disconnect the other (benzyl) side first. 

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). 

Deuteration at C-3 by Reduction of 5a.-Androstan-3-one Oxime with Lithium Aluminum Deuteride... 

Deuteration at C-3 by reduction of 5o -androstan-3-one oxime with lithium aluminum deuteride, 178... 

Excellent yields of the oximes of phenylacetaldehydes are obtained by reduction of 6-nitrostyrenes over Pd-on-C in a pyridine solvent (74,75). The technique gives yields of only about 60% when applied to aliphatic unsaturated nitrocompounds better yields are obtained in acidic media(6 5). Over 5% Rh-on-Al203 in ethanol-acetic acid-ethyl acetate, 2- 6-dinitro-styrenes are converted to 2-nitrophenylacetaldehyde oximes (13). 

Dibenz[c 1c ]azepine (32 a) is obtained by acid-mediated cyclization of 2 -(aminomethyl)bi-phenyl-2-carbaldehyde (31 a), which is generated in situ by reduction of the oxime acetal 30a.85 The acetyl 30 a and benzoyl 30c oximes behave similarly and give the dimethyl and diphenyl derivative 32 b and 32 c, respectively. 

Preparative scale reduction of oximes at a mercury or lead cathode in acid solution has been used in the conversion of the carbonyl function to amine. Originally, 30-50% sulphuric acid was used as solvent [195] but ethanol with dilute hydrochloric acid is usually satisfactory. Aliphatic and aromatic oximes give amines in 64-86% yields [196]. Aromatic ketoximes are also reducible in alkaline solution and acetophenone oxime has been converted to 1-phenylethylamine in a tri-potassium orthophosphate solution [197], The reduction of oximes in acid solution is tolerant of many other substituents as indicated by a number of examples [198, 199, 200. Phenylglyoxa monoxime in acid solution is however reduced at both the carbonyl and the oxime centres by sodium amalgam to yield 2-amino-1-phenylethanol [201]... 

The synthesis of amines from oximes is exemplified by the reduction of oxime 332 to 333 (99W032453) and of bicyclic oximes (derived from ketones 3 and 23a), for instance, of oxime 387 (Scheme 87) to amine 388 that is acylated to yield potential pharmaceutical agent 390 (92BML1147). Nucleophilic substitution of chloropyridine 384 generates morpholino derivative 385 (76IJB400). 

Sodium cyanoborohydride is the most commonly used reagent for reduction of oximes and oxime ethers. Although this reaction is highly versatile, and does not interfere with a majority of functional groups, careful control of reaction conditions is necessary. A considerable problem in the reduction, especially for aldoximes 80 (equation 57), is the reaction of initially formed A-alkylhydroxylamine 81 with the starting oxime 80. The obtained nitrone 82 is subsequently reduced to A,A-dialkylhydroxylamine 83, which was found to be a major reaction product at pH = 4 and above. This side reaction can be avoided by adjusting the pH of the reaction mixture to 3 or below. 

O-linked polymer-bound Af-substituted hydroxylamines are prepared by reduction of resin-bound oximes with borane-pyridine complex in the presence of dichloroacetic acid (Scheme 94). Other reducing systems commonly used for imine or oxime reduction are ineffective, including borane-pyridine in the presence of acetic acid. Subsequently, the A-substituted products are acylated and cleaved from the resin to afford Af-substituted hydroxamic acids 220. ... 

Synthesis of dihydrofuran derivatives by cyclization of oxime derivatives has been described. Thus, reduction of 2-quinolineacetaldoxime (26) with H2/Pt02 afforded fura-noquinoline 27 as a single product (equation 1. 4-Formy l-3-hydroxy-5-hydroxymethyl-2-methylpyridine oxime (28) in the system NaN02/HCl/H20 cyclized to furopyridine 29 (equation 13). ... 

Hydroxy-l,2,3,4-tetrahydroquinolines 304 were obtained by cyclization of oxime 2,4-dinitrophenyl ethers 303 in the presence of system NaBH3CN/NaH/l,4-dioxane (equation 131) . If the reductive cyclization was followed by oxidation with DDQ (2,3-dichloro-4,5-dicyano-p-benzoquinone) the corresponding 8-hydroxyquinolines 305 were obtained . ... 

The electrochemical reduction of phenylglyoxylate oxime in the presence of strychnine afforded the corresponding optically active amines (equation 4). Also, the electrochemical reduction of oximes by utihzing poly-L-vahne-coated graphite electrode afforded optically active amine. However, in both cases the enantioselectivities were very low. 

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