O-acylated ketoximes

The first step of the mechanism is the deprotonation of the O-acylated ketoxime at its a-position, which gives rise to the corresponding enolate. This enolate then can react via two possible pathways 1) a concerted anionic pathway in which the leaving group is directly displaced to give the isolable 2H-azirine or 2) a nitrene pathway that leads to the same 2/-/-azirine intermediate via nitrene Insertion. The nitrene pathway has not been disproved experimentally. 

TV-Substituted imines were prepared by the copper-catalyzed N-imination of boronic acids and organostannanes with O-acyl ketoximes (eq 28). In this process, both CuTC and Cu(OAc)2 were equally effective to carry out the reaction. 

Low-valent metal salts have been used to bring about reductive cleavage of oximes. Corey and Rich-man used chromium(II) acetate to convert O-acetyl ketoximes into imines, which were hydrolyzed to ketones. " Aqueous titanium(III) chloride and vanadium(II) salts also reduce oximes again, the imines are usually hydrolyzed in situ, but some hindered imines, such as compound (37), are isolable." A method of preventing hydrolysis is to carry out the reduction in anhydrous conditions in the presence of an acylating agent. The products of such reactions, when applied to oximes of enolizable ketones, are en-amides. For example, these ketoximes are converted into A/-formylenamines when heated in acetonitrile with anhydrous titanium(III) acetate and acetic formic anhydride cyclohexanone oxime gives the en-amide (38 97% Scheme 22)." This type of reduction has been used by Barton and coworkers to prepare enamides from steroidal oximes. They reported that the reaction could be performed by acetic... 

Zur Hydrierung spezieller Ketoxime mit Raney-Nickel zu Hydroxyiaminen s. Lit.5 6. i3) von O-Alkyl- bzw. O-Acyl-oximen... 

Ketoximes have been synthesized by Fujisawa using a catalytic Cul/Giignard addition to aci-nitroimi-nium chlorides, formed by O-acylation of a nitroalkane with A(,A(-dimethylchloromethyleniminium... 

Enehydroxylamines (102) are invoked as intermediates in the rearrangement of O-vinyl, acyl or aryl oximes (101) (equation 31). Varlamov and coworkers demonstrated that the heterocyclization of ketoximes (103) with acetylene in snper basic medium and in the presence of metal hydroxides proceeds by a [3,3]-sigmatropic rearrangement of the enehydroxylamine 105 of the corresponding oxime vinyl ethers 104 (equation 32). The unreactivity of 3-methyl-2-azabicyclo[3.3.1]nonan-9-one oxime (106) in the same reaction conditions was explained by its inability to isomerize to the corresponding enehydroxylamine. 

Hydroxamic acids. Oximino esters (1) are reduced by 1 equiv. of BH3 in THF at -78 to hydroxamic acids (2). The reaction involves an O to N acyl thift, (a) (b). Ketoximes are reduced completely to amines by excess diborane... 

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