Oximes reductive

Sodium cyanoborohydride has become important in biochemical appHcations that require hydrolytic stabiHty of the reducing agent and chemoselectivity, in sensitive molecules. It is also a preferred reagent for oxime reductions. 

A general one-step method for preparation of primary and secondary nitroparaffins from amines by oxidation with y -chloroperbenzoic acid in 1,2-dichloroethane has been reported (68). This method is particularly useful for laboratory quantities of a wide variety of nitroparaffins because a large number of amines are readily available from ketones by oxime reduction and because the reaction is highly specific for nitroparaffins. 

Hydrogenation of oximes to primary amines usually can be made to proceed smoothly despite the potential complications cited earlier. Many of the same considerations applicable to control of nitrile reductions hold for oxime reductions as well. Oximes, unlike nitriles, can be reduced to hydroxylamines. 

Boc-protection, oxime reduction, 128 Bond dissociation energy (BDE), hydrosilanes, 6... 

Open-chain alkanes, alkyl halide reduction, 29-31 Organosilicon hydrides bond strengths, 5-6 hypervalent silicon species, 9-11 ionic hydrogenation, 5 trivalent silicon species, 7-9 Orthoesters, reduction of, 97-99 Oxime reduction, 102... 

On treatment with dimethyl sulfoxide-acetic anhydride followed by sequential oximation, reduction, detritylation, and acid hydrolysis, a tetra-(6-0-trityl)-cyclohexaamylose was reported to afford 2-amino-2-deoxy-D-glucose, in addition to D-glucose, indicating459 that... 

Phenylacetaldehyde oxime, reduction with lithium aluminum hydride,... 

Oxidative cyclization, substituted stil-benes to phenanthrenes, 46, 91 Oximes, reduction with lithium aluminum hydride, 48, 23 Oximinomalononitrile, from nitrosation of malononitrile, 48,1 reduction with aluminum amalgam, 48,2 ... 

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. ... 

Oxime reduction is a very efficient procedure for obtaining racemic A7-hydroxy ami no acids in good yields. 19 31-361 TV-Hydroxylamine and O-protected A-hydroxylamines react smoothly and rapidly with a-oxo acid derivatives 23 to give the corresponding oximes 24. Acids 24 (R2= OH) can be reduced with NaBH3CN or LiBH3CN (Scheme 7) to give TV-hydroxyamino acids 25 (R2= OH)/31 but reaction yields are unsatisfactory for esters 24 (e.g., R2= OEt) or... 

Heterogeneous hydrogenation of the C=N bond is a very widely used synthetic process with application to small and large-scale reactions. Many of the catalysts described in other sections may also be employed, for example those based on supported rhodium, palladium etc, and Raney Nickel. This area has been reviewed extensively recently192. Hydrogenation of oximes and hydrazones results in formation of amines. Milder conditions can be used for oxime reduction if the ethylaminocarbonyl derivative is prepared in situ prior to reduction276. 

Toward this end, the process team envisioned that the oxime reduction and subsequent cyclization to form pyrrole 27 could be effected using hydrogenative conditions, which would avoid the problems associated with stoichimetric zinc salts and therefore greatly simplify the workup and isolation of the product. This strategy was successfully realized by stirring a solution of oxime 12 and P-ketoamide 26 in acetic acid under 45 psi of H2 in the presence of 10% palladium on carbon. The desired product 27 could then be isolated in 77% yield after filtration to remove the catalyst, pH adjustment to 11-13, and subsequent extraction into CH2C12. 

Fig. 5.13 Electrochemical oxime reduction. Reagents and conditions divided cell, BDD/Nb cathode, 1% NaOCH3 in anhydrous MeOH, 40°C, 3.4 Adm-2,4 h, yield = 96% (by GC)...

Oximes.—Reduction of the Beckmann fragmentation product (89) with LiAlH4 gave, after acidic (HCl) work-up, the hydrochloride (91) and the hemi-acetal (92) which may be derived from the imino-intermediate (90). Oxidation of the... 

Amino ketones, preparation, 672 reaction with otganometallic compounds, 164 reduction, 152 Aminomethylation, 673 Amino oximes, reduction, 658 Amino phenols, oxidation to quinones, 399... 

Dihalogenation of oxindole followed by alkaline hydrolysis of the 3,3-dihalooxindole has been applied to the synthesis of some isa-tins. A number of oxindoles have been treated with nitrous acid to give isatin-3-oximes. ° Reduction of the oximes to 3-aminooxindoles followed by ferric chloride oxidation gave isatins. 

---