SELECTIVE OXYFUNCTIONALIZATION OF KETONES USING 1-OXOPIPERIDINIUM SALT

4-Methoxy-2,2,6,6-tetramethyl-1-oxopiperidinium chloride, made from th e corresponding 1-piperidinyloxyl radical and chlorine gas, was used a s an oxyfunctionalizing reagent for a number of enolizable ketones. Re gioselective alpha- or gamma-oxygenated carbonyl compounds were obtain ed smoothly at ambient temperature in moderate to good yields. Oxyfunc tionalization of (+)-carvone and (-)-carvone proceeded stereoselective ly, and provided cis-product (5R, 6S)- and (5S, 6R)-2-cyclohexen-1-one s, respectively. Interestingly, unsymmetrical ketones afforded isomeri c alpha- and alpha'-oxygenated ketones, while allyl ketones gave the r egiospecific gamma-oxygenated products with the migration of the doubl e bond in the allylic group.