Copper-catalyzed amination of alkenes and ketones by phenylhydroxylamine

Abstract

The catalytic activity of a number of copper complexes and salts toward allylic amination of alkenes using phenylhydroxylamine as the nitrogen fragment donor has been investigated. The best catalyst is CuCl₂·2H₂O, which produces moderate yields of allylamines with high regioselectivity resulting from double bond transposition. A mechanism similar to that for the molybdenum and the FePc systems is proposed. The first step in the catalytic cycle is the formation of nitrosobenzene from the oxidation of phenylhydroxylamine by Cu(II). The next step is an ene reaction of the alkene with PhNO to produce an allylhydroxylamine, which is then reduced to the allylamine product by Cu(I), thus regenerating Cu(II). The same system can also transfer the nitrogen fragment to the α-carbon of cyclic ketones; this is accompanied by dehydrogenation in some cases to produce α-aminated, α,β-unsaturated ketones.