Cu(I)−Amido Complexes in the Ullmann Reaction: Reactions of Cu(I)−Amido Complexes with Iodoarenes with and without Autocatalysis by CuI

Abstract

A series of Cu(I)−amido complexes both lacking ancillary ligands and containing 1,10-phenanthroline (phen) as ancillary ligand have been prepared. These complexes react with iodoarenes to form arylamine products, and this reactivity is consistent with the intermediacy of such complexes in catalytic Ullmann amination reactions. The stoichiometric reactions of the Cu(I)−amido complexes with iodoarenes are autocatalytic, with the free CuI generated during the reaction serving as the catalyst. Such autocatalytic behavior was not observed for reactions of iodoarenes with copper(I) amidates, imidates, or phenoxides. The selectivity of these complexes for two sterically distinct aryl halides under various conditions imply that the autocatalytic reaction proceeds by forming highly reactive [CuNPh2]n lacking phen. Reactions with radical probes imply that the reactions of phen-ligated Cu(I)−amido complexes with iodoarenes occur without the intermediacy of aryl radicals. Density functional theory calculations on the oxidative addition of iodoarenes to Cu(I) species are consistent with faster reactions of iodoarenes with CuNPh2 species lacking phen in DMSO than reactions of iodoarenes with LCuNPh2 in which L = phen. The free-energy barrier computed for the reaction of PhI with (DMSO)CuNPh2 was 21.8 kcal/mol, while that for the reaction of PhI with (phen)CuNPh2 was 33.4 kcal/mol