We report that boric acid, BO3H3, is a good precatalyst for the BH3-catalyzed hydroboration of esters using pinacolborane as a borylation agent. Using microwave irradiation as an energy source, we demonstrated that a dozen esters were converted into the corresponding boronate ethers in good yields. It was also possible to use boric acid as a precatalyst to reduce carbonates and alkynes. Considering the hazardous and pyrophoric nature of BH3 solutions, boric acid proves to be a safe and green precatalyst for the metal-free reduction of unsaturated species.

Boric acid is a safe and green precatalyst for BH3-catalyzed hydroboration of esters, enabling metal-free reduction of unsaturated species without using toxic BH3 solutions.

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Boric acid as a precatalyst for BH3-catalyzed hydroboration

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