Isodesmic C-H Borylation: Perspectives and Proof of Concept of Transfer Borylation Catalysis

The potential advantages of using arylboronic acids or esters as boron source in the C-H borylation are discussed. The concept is showcased by using commercially available and air-stable 2-mercaptopyridine as a metal-free catalyst for the transfer borylation of heteroarenes, using furylboronic acid catechol ester as the borylation agent. The catalysis can be performed in air using unpurified solvent and shows a unique functional group tolerance among C-H borylation reactions, tolerating notably alkene and alkyne functional groups. The computational investigation of the mechanism is also described.