Acetophenone oxime, reduction with

Acetophenone oxime, reduction with lithium aluminum hydride, 48,23... 

The present procedure was developed from those of Wallach and Freylon, based upon the general method discovered by Leuckart. a-Phenylethylamine also can be prepared satisfactorily by the reduction of acetophenone oxime with sodium and absolute alcohol or sodium amalgam, but the reagents are more expensive and the processes less convenient. The amine has been obtained by reducing acetophenone oxime electro-lytically, by reducing acetophenone phenylhydrazone with sodium amalgam and acetic acid, from a-phenylethyl bromide and hexamethylenetetramine, and by the action of methyl-magnesium iodide upon hydrobenzamide, as well as by other methods of no preparative value. 

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 preparation of oximes from olefins is a valuable approach for the synthesis of nitrogen-containing compounds such as amino acids and heterocycles. Okamoto and colleagues have reported that a catalytic reduction-nitrosation of styrenes 31 with ethyl nitrite and tetrahydroborate anion by the use of bis(dimethylglyoximato)cobalt(II) complex afford the corresponding acetophenone oximes 32 (Scheme 23). 

The same authors also found the catalytic effect of la in the reduction of acetophenone oxime O-methyl ether, showing that the use of 10 mol% of la afforded product amine with 52% ee [81], Polymer-supported OABs were also very effective for the same reduction to give (S)-l-phenylethylamine with 99% ee [31]. Interestingly, the absolute configurations of the amines formed depend on the geometry of the oxime ethers the E oxime led to the S amine, while the Z oxime gave rise to the R amine (Scheme 11.18) [82],... 

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. 

Less useful results are obtained with aminoalcohol 2.24, except in the reduction of the oxime ether of acetophenone by NaBILt/ZnClt), which leads to (Sy 1 -phenethylamine with an excellent enantiomeric excess [575, 601,1102],... 

Based on a comparative study for asymmetric reduction of oxime ethers of acetophenone and 2-hepitanone using different classes of OABs, such as la, 2a, and 6a, Cho and Ryu reported the 6a-induced borane reduction of ketoxime O-trimethylsilyl ethers in moderate to good enantioselectivities (Scheme 11.19) [83a, bj. Similarly, ben-zylic amine derivatives were obtained with high enantioselectivities by stoichiometric reduction of oxime ethers using ent-6a-BHj or la-BH (Scheme 11.20) [84-86],... 

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