Ketoxime Derivatives

Itsuno and co-workers reported the successfid asymmetric reduction of aromatic ketone oidme Oalkyl ethers with 1.2 equiv. of la generated in situ from (S)-diphenyl valinol and excess borane-THF to produce the corresponding amines in 69-99% ee 

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The ketoxime derivatives, required as starting materials, can be prepared from the appropriate aromatic, aliphatic or heterocyclic ketone. Aldoximes (where R is H) do not undergo the rearrangement reaction, but rather an elimination of toluenesulfonic acid to yield a nitrile. With ketoxime tosylates a Beckmann rearrangement may be observed as a side-reaction. 

Closure of the oxadiazole ring is still achieved through cycloaddition between pyridine iV-oxides and isocyanates, affording adducts such as 142 (Scheme 38) <1995T6451>. Nonaromatic imine fV-oxides exhibited similar reactivities, since azasugar-derived fV-oxides as a mixture of 143 and 144 underwent cycloaddition reactions in the presence of phenyl isocyanate or trichloroacetonitrile. Compounds 145 and 146 (Scheme 39) were obtained from the aldoxime W-oxide 143 two other regioisomeric heterocycles arose from the ketoxime derivative 144 <1996T4467>. 

To reduce the likelihood of isocyanate-induced toxicity, some commercial companies that manufacture and use isocyanates in coating systems mask the electrophilic character of this functional group by converting it into a ketoxime derivative, as represented by 10. 

It would be attractive from both mechanistic and preparative standpoints to obtain pyrroles by condensation of acetylene with ketoxime derivatives or analogs, e.g., their ethers or hydrazones, i.e., to realize the... 

The ketoxime derivative fluvoxamine (12) is a newer antidepressant thought to potentiate the action of 5-hydroxytryptamine76. Oxacillin (13), cefuroxime (14) as well as the monobactam aztreonam (15) represent potent antibacterial agents of the beta-lactam type77. The aldoxime pralidoxime (16) and a number of bi.v-quarternary oximes, such as obidoxime (17), can be used as reactivators of the phosphorylated esteratic site of acetylcholinesterase that occurs in the presence of organophosphate inhibitors78,79. 

Ketoxime derivatives (89a R, R = alkyl, aryl) undergo the usual acid-catalyzed Beckmann rearrangement with great ease.254, 259... 

Scheme11.17 la-induced borane reduction of ketoxime derivatives.

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