Metal-free photocatalyzed homo- and cross-dimerizations of α-hydroxyl ketones via dual C(sp 3 )–H functionalization: synthesis of 2,3-dihydroxyl-1,4-butanediones

The dimerizations of α-hydroxyl ketones at the α-carbon site have been realized in the fashion of homo- and cross-coupling, leading to the synthesis of a variety of 2,3-dihydroxyl-1,4-butadiones. This dual C–H coupling reaction proceeded under transition metal-free conditions to enable the construction of a new C(sp 3 )–C(sp 3 ) bond, expanding the application space of α-hydroxyl ketones and analogous model compounds from biomass. Mechanistic studies using electron paramagnetic resonance (EPR) revealed the formation of a key α-hydroxyl carbon-radical in the reactions.