Boronic acids

Boronic Acids are a class of organic compounds that contain a boron atom bonded to an oxygen atom and a hydrogen atom (or a substituted alkyl group). The general formula for boronic acids is BR2OH, where R can be a variety of substituents.

History

The first boronic acid was synthesized in 1860 by the French chemist Charles-Adolphe Wurtz. He reacted boric acid with phenylmagnesium bromide to produce phenylboronic acid. Since then, boronic acids have been extensively studied and used in a variety of applications.

Structure and Properties

Boronic acids are characterized by a trigonal planar geometry around the boron atom. The boron-oxygen bond in boronic acids is polar, with the boron atom bearing a partial positive charge and the oxygen atom bearing a partial negative charge. This polarity makes boronic acids susceptible to nucleophilic attack. Boronic acids are also capable of forming stable complexes with diols, a property that is exploited in many of their applications.

Synthesis

Boronic acids can be synthesized through several methods. The most common method is the reaction of a Grignard reagent or an organolithium reagent with a borate ester. Other methods include the hydroboration of alkenes and the reaction of boron trichloride with a Grignard or organolithium reagent.

Applications

Boronic acids have a wide range of applications in organic chemistry. They are used as catalysts in a variety of reactions, including the Suzuki-Miyaura coupling reaction, which is used to form carbon-carbon bonds. Boronic acids are also used in the synthesis of heterocyclic compounds, which are important in the pharmaceutical industry. In addition, boronic acids have been used as sugar sensors due to their ability to form stable complexes with diols.

See Also

• Boronic esters
• Suzuki-Miyaura coupling
• Grignard reagents
• Organolithium reagents