Intermolecular Oxidative Radical Addition to Aromatic Aldehydes: Direct Access to 1,4- and 1,5-Diketones via Silver-Catalyzed Ring-Opening Acylation of Cyclopropanols and Cyclobutanols

A novel silver-catalyzed
ring-opening acylation of cyclopropanols
and cyclobutanols is described. The reaction proceeds under mild and
neutral conditions and provides a facile access to nonsymmetric 1,4-
and 1,5-diketones in promising yields with broad substrate scope.
Mechanistic studies including DFT calculations suggest the involvement
of an uncommon water-assisted 1,2-HAT process, which is strongly exothermic
and thus promotes addition of carbon radicals to aldehydes. In contrast
to traditional reductive radical addition protocols, this work represents
the first example of the intermolecular oxidative radical addition
to aldehydes, thus offering a novel strategy for the direct synthesis
of acyclic ketones from readily accessible aldehydes.