Reactivity Tuning for Radical-Radical Cross-Coupling via Selective Photocatalytic Energy Transfer: Access to Amine Building Blocks

Reductive N-O bond cleavage has been widely explored for providing either N or O radical species for various coupling processes. Despite significant advances, this photoredox pathway is less appealing due to poor atom-economy, owing to the loss of one fragment during the transformation. In this regard, homolytic N-O bond cleavage by an energy transfer pathway to provide two key radicals would be highly desirable for overcoming the limitations with the use of one fragment. We report an exclusive energy transfer approach for the development of a challenging radical-radical C(sp3)-N cross-coupling process by reactivity-tuning of the catalytic system. The homolytic N-O bond cleavage of oxime esters in the presence of an Ir complex produces acyloxy and iminyl radicals, which underwent decarboxylative cross-coupling to yield valuable imines (typically 0.25 mol% cat. and 1 h reaction time). Extensive photophysical and electrochemical measurements, as well as DFT studies, were carried out to probe the mechanism a...