To support clients conducting Suzuki-Miyaura cross-coupling reactions for biaryl synthesis, as well as other synthesis reactions, ARCI stocks boronic acid/ester intermediates. Our catalogue includes many novel and rare intermediates, available in a range of standardized quantities.
A chemical database containing CAS number, synthesis references, physical properties (melting/boiling point, refractive index, density and solubility) for more than 2,000 boronic acids, boronic acid esters and trifluoroborates is available on our website.
Boron—the beloved oddball of the periodic table—can do some unique chemistry, thanks to its empty p-orbital. This has made boronic acids and boronate esters indispensable components in many compounds, such as in partners for Suzuki cross-coupling reactions, in polymers, and even in a few drugs, such as the cancer therapies bortezomib (Velcade) and ixazomib (Ninlaro). But, while there are a few ways to make boronic acids and boronate esters, none are trivial.
’s group at Scripps Research Institute, California, has now come up with a for converting carboxylic acids into a boronate esters and boronic acids (2017, DOI: ).
The method works on primary, secondary, and tertiary carboxylic acids, as well as peptidic and even natural product-derived substrates. It also tolerates a broad range of functional groups, so it can be used in the final steps of the synthesis of a densely functionalized molecule. For example, Baran’s group prepared a boronic acid analog of the antibiotic vancomycin, a compound that is packed with stereocenters and functional groups. The reaction conditions modified only vancomycin’s carboxylic acid.
To convert a carboxylic acid to a boron compound, Baran’s team first transforms it into a redox-active -hydroxyphthalimide ester. This compound then undergoes decarboxylative borylation in the presence of a nickel catalyst, a bipyridine ligand, and bis(pinacolato)diboron to make the boronate ester. These two reactions can be carried out in a single pot. The boronate esters can then be hydrolyzed to the corresponding boronic acids.
In another demonstration of the method’s power, Baran’s group teamed up with scientists at to make boronic acid analogs of human neutrophil elastase inhibitors. Neutrophil elastase is an important target in lung diseases, such as cystic fibrosis and chronic obstructive pulmonary disease. Calibr had been working with inhibitors that had failed Phase II clinical trials because of potency issues. Baran group’s chemistry added a boronic acid to these molecules and the resulting compounds proved to be far more potent than the parent compounds in tests, including enzyme assays. Calibr is currently studying the in vivo activity of the compounds.
Boronic acids and their esters are highly popular synthetic intermediates in organic synthesis for their ease and efficiency of conversion to other functional groups, in metal-catalyzed cross-coupling reactions and for their unique biochemical activity.
A new class of air-stable boronic acid derivatives is trifluoroborates, which are offering a unique alternative to most boronic acids, esters and organoboranes for use in Suzuki-Miyaura and other transition-metal-catalyzed cross-coupling reactions.
As inhibitors of serine proteases, boronic acids inhibit therapeutically relevant proteases and proteasomes. FDA has approved the first boron-containing drug, bortezomib (Velcade) for the treatment of multiple myeloma and mantle cell lymphoma.
Boronic esters (RB(OR)2), also referred to as boronate esters, are formed between a boronic acid and an alcohol. Boronate esters are stable compounds, although the -C-B- bond of boronic ester is slightly longer than C-C single bonds. Boronic acid esters can undergo saponification and racemize optically active compounds. Boronic acid esters coordinate with basic molecules to form stable tetra-coordinated adducts. Boronic acid esters are considered as compounds for the designing of new drugs and drug delivery devices, more particularly as boron carriers for neutron capture therapy.
Boronic esters are very easy to purify and characterize. They have enhanced reactivity, higher compatibility with many reagents, better solubility in organic solvents, and are also used as good protecting groups to eliminate unwanted side reactions. Boronic acid ester molecules are used in pharmaceuticals, agrochemicals, and high-tech materials.
With their excellent ability to construct C-C bonds via metal-catalyzed cross coupling, boronic esters have received much attention for use in organic synthesis. The boronic esters are widely used for carrying out cross coupling reactions. Boronic acid esters are used in the Suzuki-Miyaura coupling reaction for synthesizing unsymmetrical biaryls, which has wide use in pharmaceuticals and agrochemical industries. Chiral alpha-Haloalkylboronic esters as reagents for asymmetric synthesis (reviewed in Boronic Esters in Asymmetric Synthesis, Matteson, D. S. J. Org. Chem., 2013, 78 (20), 1000910023) have been reported to yield diastereomeric ratios exceeding 1000. (alpha-Amidoalkyl)boronic acids include the biochemically significant serine protease inhibitors, which are used for the treatment of multiple myeloma and mantle cell lymphoma.