Oximes dissolving metals

Catalytic reduction of fluormated aliphatic and aromatic nitro compounds to give oximes and amines was described previously, as was the use of dissolving metals to prepare amines [Si] Refmement of these techniques has resulted in optimized yields and, as indicated in equations 69 and 70, in selective reductions [S6, 87]... 

Electrochemical reduction of camphor-and norcamphoroxime at a Hg cathode proceeds with a high degree of stereoselectivity to give products of opposite stereochemistry to those formed in the dissolving metal (Na-alcohol) reduction of the oximes. The electrolyses are proposed to proceed by a kinetically controlled attack by the electrode on each oxime from the less hindered side (Fig. 62) [348]. In contrast, the corresponding N-phenyl imines yield products of the same stereochemistry as those isolated from a dissolving metal reduction. Cyclic voltammetry and polarographic data point to RH and intermediates in this case that are proto-nated from the least hindered side [349]. 

Electrochemical reductions of camphor oxime (R = Me) and norcamphor oxime (R = H) at a mercury cathode proceed with a high degree of diastereoselectivity (equation 3) . The products are in fact of opposite stereochemistry to those formed in dissolving metal (sodium-ethanol) reductions of the oximes. 

Dissolving metals have been used as reducing agents in organic synthesis for well over a century and for many years metal-alcohol or metal amalgam-water systems were the principal methods employed for the reduction of aldehydes and ketones to primary and secondary alcohols, respectively. The same reagents were employed for the reduction of imines and oximes to the corresponding amines. Catalytic hy-... 

The stereochemical course of these, and other similar reductions, led Barton to suggest that dissolving metal reductions of ketones and oximes to secondary alcohols and primary amines would lead to mixtures of products rich in the thermodynamically more stable product. However, in the early 1960s a number of reports appeared in which the reduction of ketones gave primarily the thermodynamically less stable epimeric alcohol. These observations have prompted a continuing series of investigations into the mechanism of these reductions. 

The reduction of oximes to primary amines by dissolving metals, usually Na-alcohol, is an established synthetic procedure which has been employed for many years. Although in some cases LAH reduction is superior, the reduction of many oximes with LAH leads either to aziridines or Beckman-type rearrangements. ... 

Dissolving metal reduction of the oxime and hydrolysis gave lR,3R-3-aminocyclo-pentane-1-carboxylic acid, 7.41. An identical approach was used to prepare cyclohexane derivatives. Reaction of 7.129 " with hydroxylamine76b.77 nd subsequent... 

The principle of solvent extraction in refining is as follows when a dilute aqueous metal solution is contacted with a suitable extractant, often an amine or oxime, dissolved in a water-immiscible organic solvent, the metal ion is complexed by the extractant and becomes preferentially soluble in the organic phase. The organic and aqueous phases are then separated. By adding another aqueous component, the metal ions can be stripped back into the aqueous phase and hence recovered. Upon the identification of suitable extractants, and using a multistage process, solvent extraction can be used to extract individual metals from a mixture. 

Benzaldehyde reacts with nitroethane in an alcohol solution with n-butylamine catalyst to produce a crystalline substance called a nitroalkene. This nitroalkene can then be reduced by means of iron and HCl to produce phenylacetone. The reduction is similar to the use of activated aluminum in the reaction to produce methamphetamine without the bomb, in that the metal, in this case iron, dissolves and produces hydrogen which reduces the nitroalkene. It is not as complicated as it sounds, and is pretty easy to do. The nitroalkene is first reduced to phenylacetone oxime, which is then hydrolyzed to phenylacetone. 

In liquid-liquid systems, a chemical reaction is encountered for three distinct purposes. Firstly, the reaction may be a part of the process, such as nitration and sulphonation of aromatic substances, alkylation, hydrolysis of esters, oximation of cyclohexanone, extraction of metals and pyrometallurgical operations involving melts and molten slag. Secondly, a chemical reaction is deliberately introduced for separation purposes (e.g. removal of dissolved acidic solutes from a variety of hydrocarbons). Finally, the yield and the rate of formation of many single phase reactions are affected and often can be favourably increased by the deliberately controlled addition to the reaction system of an immiscible extractive phase, whose major purpose is to extract the product from the reactive phase. Such operations are sometimes referred to as "extractive reactions" and have been discussed previously in some detail (14-17). 

If other metallic salts which form precipitates with ammonia are present in such amount that they interfere with the recognition of the benzoin-oxime test, their precipitation can be prevented by the addition of sodium potassium tartrate. The sensitivity of the copper test is, however, somewhat reduced by considerable amounts of tartrate. Large amounts of ammonium salts also prevent the complete precipitation of the green Cu-benzoinoxime. Consequently, if the test solutions are strongly acid or contain ammonium salts, a drop should be evaporated and ignited. The benzoinoxime test is carried out after the residue has been dissolved in a drop of dilute hydrochloric acid. 

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