USE OF KETOXIME DERIVATIVES TO PREPARE ALPHA-ACETOXY KETONES

The O-acetyl derivatives of oximes from 4-heptanone (10), deoxybenzoin (11), dibenzyl ketone (12), cyclohexanone (13), 2-methylcyclohexanone (38), and p-nitrobenzyl p-methoxybenzyl ketone (37) have been prepared. Successive reactions of each of these oxime acetates with trimethyloxonium fluoroborate, triethylamine, and aqueous acid yielded an α-acetoxy ketone. Evidence is presented to support the idea that these transformations proceed via a facile Claisen-type rearrangement of an intermediate N-acetoxyenamine. In the cases of cyclohexanone and 2-methylcyclohexanone, a related rearrangement was effected by reaction of the ketones with the hydrochloride salt of O-acetyl-N-methylhydroxylamine (28). With unsymmetrical ketones, the proportions of structurally isomeric α-acetoxy ketones produced were not influenced by the stereochemistry of the starting oxime acetate. © 1969, American Chemical Society. All rights reserved.