Visible light-mediated syntheses of unsymmetrical methylene-bridged bis -heterocycles via an alkoxy radical relay reaction

Efficient and versatile syntheses of methylene-bridged bis -heterocycles that embody dihydroisoxazoline/pyridine or dihydroisoxazoline/quinoline pairings are described. These proceed under mild conditions and involve a visible light-mediated radical-relay sequence that begins with the homolysis of O–H bonds contained within β , γ -unsaturated oximes to generate oxygen-centred radicals that add to the tethered olefin. The ensuing carbon-centered radical is then trapped by an added N -heteroarenium salt. The results suggest that the radical-chain is sustained by hydrogen atom transfer between in situ generated methoxy radicals and oxime O–H bonds. Such outcomes provide new insights into alkoxy radical-mediated transformations promoted by visible light as well as access to new molecular scaffolds likely to be useful in a variety of settings.