Transition metal-free visible light photoredox-catalyzed remote C(sp3)-H borylation enabled by 1,5-hydrogen atom transfer

The borylation of unreactive carbon-hydrogen bonds is a valuable method for transforming feedstock chemicals into versatile building blocks. Here, we describe a transition metal-free method for the photoredox-catalyzed borylation of unactivated C(sp(3))-H bond, initiated by 1,5-hydrogen atom transfer (HAT). The remote borylation was directed by 1,5-HAT of the amidyl radical, which was generated by photocatalytic reduction of hydroxamic acid derivatives. The method accommodates substrates with primary, secondary and tertiary C(sp(3))-H bonds, yielding moderate to good product yields (up to 92%) with tolerance for various functional groups. Mechanistic studies, including radical clock experiments and DFT calculations, provided detailed insight into the 1,5-HAT borylation process. Alkyl boronic esters are commonly used building blocks in organic synthesis, causing efficient C-H borylation methods to be in high demand. Here, the authors develop a method for the photoredox-catalyzed borylation of unreactive C(sp(3))-H bonds, mediated by amidyl radicals to achieve C-H borylation at the & lambda; position of carbonyl compounds.