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

The potential advantages of using arylboronic esters as boron sources in C–H borylation are discussed. The concept is showcased using commercially available 2-mercaptopyridine as a metal-free catalyst for the transfer borylation of heteroarenes using arylboronates as borylation agents. The catalysis shows a unique functional group tolerance among C–H borylation reactions, tolerating notably terminal alkene and alkyne functional groups. The mechanistic investigation is also described.