Acetophenone methyl oxime, reduction

DFT has been used to investigate the mechanism of enantioselective borane reduction of -acetophenone 0-methyl oxime, using a stable chiral spiroborate ester. ... 

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. 

It is interesting that Didier also studied the reduction of anti-acetophenone oxime methyl ether (Scheme 17.3)36 and again observed that m-aminoindanol yielded one of the highest selectivity (95% ee). However, a stoichiometric amount of amino alcohol was needed to achieve high degrees of asymmetric induction. Use of a catalytic amount of amino alcohol resulted in a considerable decrease in product enantioselectivity. 

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],... 

Application of variant A to the reduction of anft-[rmg-U- " C]acetophenone oxime methyl ether (55) afforded (S)-l-[ring-U- " C]phenylethylamine 1561 in 70% radiochemical yield and 96% e.e.. In contrast to values published in the literature, enantiomeric excesses were only 80% when variant B was employed in the reduction of 3 -methoxy [carbonyl- " C ] -acetophenone oxime methyl ether (57), so that the material had to be further purified through a diastereomeric salt. ... 

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