Gold-Photoredox-Cocatalyzed Tandem Oxycyclization/Coupling Sequence of Allenols and Diazonium Salts with Visible Light Mediation

Abstract

The room temperature radical cycloetherification/arylation cascade of allenols and diazonium salts has been accomplished via a combination of gold and photoredox catalysis to provide 2,3,4-trisubstituted-2,5-dihydrofurans. The functionalized oxacycle formation sequence is chemo- and regioselective for the cycloetherification and for the position that bears the aryl moiety after the cross-coupling. Mechanistic investigations revealed that this transformation proceeds through an initial oxidation of gold(I) to a phenyl gold(III) complex, which, upon coordination to the allene, catalyzes its cyclization and leads to the coupling product after a reductive elimination regenerating Au(I). (Figure presented.).