Photoinduced Dehydrogenative Borylation via Dihydrogen Bond Bridged Electron Donor and Acceptor Complexes

Air-stable amine- and phosphine-boranes are discovered as donors to integrate with pyridinium acceptor for generating pho-toactive electron-donor-acceptor (EDA) complexes. Experimental results and DFT calculations suggest a dihydrogen bond bridging the donor and acceptor. Illuminating the EDA complex enables an intramolecular single electron transfer to give boron-centered radical for dehydrogenative borylation with no need of external photosensitizer and oxidant. The deproto-nation of Wheland-like radical intermediate rather than its generation is believed to determine the very good ortho-selectivity based on DFT calculations. A variety of α-borylated pyridine derivatives have been readily synthesized with good functional group tolerance.