Author: Dr Holly Bonfield

In 2022, the MacMillan group reported a method for the decarboxylative borylation of (hetero)aryl acids, which is enabled by copper charge transfer catalysis.¹

This chemistry has been successfully reproduced in-house using our 365 nm LEDs. A one-pot borylation/Suzuki sequence was also demonstrated.

The aryl carboxylic acid is deprotonated, the copper(I) pre-catalyst combines with the resultant aryl carboxylate and a single-electron oxidant (NFSI), generating a Cu(II)-carboxylate complex.

Upon excitation with 365 nm light, this complex undergoes ligand to metal charge transfer in its excited state.

It is this process that then enables decarboxylation, generating the intermediate aryl radical, and simultaneously regenerating the copper(I) catalyst. Borylation then occurs through reaction with an activated metal boronate (generated in situ from B₂Pin₂ and the metal salt additives), delivering the desired borylated product.

References

1. https://macmillan.princeton.edu/wp-content/uploads/decarboxylative-borylation.pdf