5-(Hydroxymethyl)thiophene-3-boronic Acid | CAS 1268683-45-9 | ≥98%

5-(Hydroxymethyl)thiophene-3-boronic Acid ([5-(hydroxymethyl)thiophen-3-yl]boronic acid) is a bifunctional thiophene building block: a Suzuki-active boronic acid at the 3-position and a primary hydroxymethyl group at the 5-position of an electron-rich thiophene, the boron coupling while the alcohol stays free for further functionalisation.

May contain small amounts of the corresponding boroxine (cyclic boronic acid anhydride). Under aqueous or basic coupling conditions the acid and boroxine forms re-equilibrate, so anhydride content is not normally material for Suzuki–Miyaura use.

Applications and Reactions

• Suzuki–Miyaura coupling: couples as a heteroarylboronic acid with aryl and heteroaryl halides to give hydroxymethyl-thienyl-substituted (hetero)aromatics — reported, for instance, in coupling onto a chloro-azaheterocycle to build a kinase-inhibitor scaffold.
• 3-(β-)thienyl boronic acid: the boron occupies the thiophene 3-(β-)position; as with heteroarylboronic acids generally, its protodeboronation behaviour is condition-dependent.
• Orthogonal hydroxymethyl handle: the primary alcohol is a second point of diversification — oxidised toward formyl or carboxyl analogues, or converted to ethers and esters, before or after coupling.

Further Reading

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