3-Thienylboronic Acid | CAS 6165-69-1 | ≥98%

3-Thienylboronic Acid (thiophene-3-boronic acid) is a sulfur-containing heteroarylboronic acid for installing the thiophen-3-yl unit into aromatic, heteroaromatic, and π-conjugated frameworks.

May contain small amounts of the cyclic anhydride 3-thienylboroxine. Under aqueous or basic coupling conditions the two forms re-equilibrate and the impact on yield is minor.

Applications and Reactions

• Suzuki–Miyaura cross-coupling: couples with aryl, heteroaryl, or alkenyl electrophiles to give thiophen-3-yl biaryls, heterobiaryls, styrenyl thiophenes, and extended heteroaryl products.
• Heteroaryl pharmaceutical intermediates: introduces a thiophene fragment into heteroaryl scaffolds used in medicinal-chemistry and agrochemical intermediate synthesis.
• Porphyrin functionalisation: documented as a Suzuki partner for thienyl-substituted porphyrin synthesis, where the thiophene unit modifies the electronic structure of the macrocyclic chromophore.
• Imidazole scaffold construction: used to prepare thiophen-3-yl-substituted imidazole derivatives by cross-coupling, giving access to N/S-heteroaryl frameworks for research libraries.
• Conductive polymer precursor: electropolymerises to poly(3-thienylboronic acid), combining a polythiophene-type backbone with pendant boronic acid groups.
• Boronate–diol recognition: the boronic acid group enables reversible interaction with saccharides and other diol-containing molecules in chemosensitive polymer and electrode systems.

Further Reading

For boronic acids, boronic esters, protodeboronation, boroxine content, and Suzuki–Miyaura reagent selection, see NorrChemica's Lab Journal guide: Choosing Your Boron Source for Suzuki–Miyaura Coupling