Alkoximes

Direct dehydrogenation of oximes is also possible, particularly for sterically hindered nitrile oxides. The most successful oxidizing agents are alkaline hypobromite and NBS in the presence of base, the latter being valuable when basic groups are present. Lead tetraacetate and alkaline hypochlorite have also been employed, but the yields are lower. The formation of furoxans from the reaction of alkoximes with nitrogen oxides is believed to proceed via the corresponding nitrolic acids. 

ROH.366,367 A wide range of alkoximes have been surveyed for this reactivity, the reaction proceeding via deaquation and elimination of ROH with no net redox change occurring at the metal centre.366"368... 

Holland, D. O. Preparation of 2-alkyl-l,4-naphtaquinone-4-carboxy-alkoximes. British Patent 621,934 (April 22, 1949 to Glaxo Laboratories Ltd), 1949. 

In the case of a carbohydrate-aldehyde source, an isomeric mixture of products is to be expected, consisting mainly of the F-isomcr and some of the Z-form of the open-form sugar alkoxime and only minor amounts of the two anomeric pyranosyl oximes (Fig. 26) [179],... 

Fig. 26 An isomeric mixture is expected when preparing sugar alkoximes from a carbohydrate-aldehyde source...

Some aspects of m.s. research in steroids have been briefly reviewed,"" with particular emphasis on the use of trimethylsilyl ethers of sterols, their hydroxy derivatives, and alkoximes of pregnan-20-ones. The trimethylsilyl ethers of 6-hydroxy-steroids influence fragmentation patterns, giving characteristic ions particularly when a 3-hydroxy- (TMS) or 3-oxo-group is also present." Experiments with deuterium-labelled materials " have confirmed the major... 

Alkenes s. Ethylene derivatives Alkoxides s. Alkali alkoxides Alkoximes... 

Sodium hydride 1-Sulfonyloxy-l-alkoximes from hydroxamic acid esters... 

Acylamino-l-thioethers N-Acylcarboxylic acid thioamides Acylisothiocyanates Cyanothioformic acid esters Methylthiomethyl iminoesters l-(Organothio)alkoximes... 

Acoxylamines (N-Acylalkoxylamines) 1-Alkoxy-l-alkoximes Amide acetals... 

Alcohols from oxo compds. 20 eqs. NaBH4 added to a soln. of 5 eqs. ZrC in THF at room temp, under N2, a soln. of 4 eqs. acetophenone in the same solvent added, and the mixture stirred at room temp, for 5 h - 1-phenylethanol. Y 96%. ZrCl4 is inexpensive, easy to use, and does not affect ar. nitro compds. and bromides. F.e., also reduction of carboxylic acids, esters and halides to prim, alcohols, and amides, oximes, alkoximes, nitriles, and imines to amines, s. S. Itsuno et al.. Synthesis 1988, 995-6. 

---