3,5-Dibromophenylboronic Acid

Technical Specifications

Product Description & Scientific Applications

3,5-Dibromophenylboronic Acid is a trifunctional arylboronic acid building block with two electronically equivalent aryl bromide handles.

Applications and Reactions

Chemoselective and sequential Suzuki–Miyaura coupling to C3-symmetric arenes: the C–B bond couples with aryl, heteroaryl, and alkenyl halides or triflates under Pd/base to give biaryl, heterobiaryl, and styrene-type products. Coupling first at boron while keeping both Ar–Br bonds is not the automatic outcome of generic conditions, because the equivalent C3 and C5 bromides are themselves oxidative-addition sites; it requires designed conditions (catalyst/ligand, base, electrophile stoichiometry, temperature) that favour transmetalation over oxidative addition into C–Br. With the bromides retained, they serve as handles for further Pd-catalysed coupling (Suzuki, Stille, Negishi, Sonogashira, Heck, Buchwald–Hartwig, Miyaura borylation); because the two are equivalent, the stoichiometry of the second electrophile — not site discrimination — sets mono- versus di-substitution, giving a 3-substituted-5-bromo or a symmetric 3,5-disubstituted arene. Three identical aryls at C1/C3/C5 give a C3-symmetric 1,3,5-triarylbenzene with 120° three-fold geometry — a core motif for star-shaped π-conjugated oligomers, tripodal ligands, discotic liquid crystals, and oligophenylene precursors to nanographenes and hexabenzocoronenes by Scholl cyclodehydrogenation.

AB₂ Suzuki polycondensation to hyperbranched poly(m-phenylene)s: with no external partner, the single B(OH)₂ ("A") and two equivalent Ar–Br ("B") functions make it an AB₂ monomer that self-condenses under Pd catalysis to hyperbranched poly(m-phenylene)s with a bromide-terminated periphery. Related AB₂ monomers (e.g. m-terphenyl types under Pd(OAc)₂/SPhos) reach higher molecular weight and lower dispersity via a pseudo-chain-growth, catalyst-transfer pathway.

Protected-boronate lithiation / electrophile-trapping chemistry: the dibromoarylboron framework is related to protected dihalophenylboronate systems (e.g. dihalophenyl dioxazaborocines) used in low-temperature lithiation followed by electrophile trapping, a route to functionalised dihalophenylboronic acid derivatives when the boron centre is suitably protected. This chemistry is best described for suitably protected boronate systems; the unprotected B(OH)₂ form should not be assumed to tolerate organolithium conditions without a substrate-specific procedure.

Chan–Lam-type C–N and C–O coupling: class-level arylboronic-acid chemistry.

Petasis borono-Mannich reaction: class-level arylboronic-acid chemistry. The boronic acid acts as the aryl donor in a three-component coupling with an amine and an aldehyde, glyoxylic acid, or α-hydroxy aldehyde partner to give arylated amines.

Reversible boronate ester formation with diols: class-level arylboronic-acid chemistry. As an arylboronic acid, forms reversible covalent boronate esters with cis-1,2- and 1,3-diols, saccharides, and catechols in aqueous media. The two meta-Br substituents are electron-withdrawing by Hammett σₘ values and are expected to lower the boronic-acid pKa relative to the unsubstituted phenylboronic-acid baseline (~8.8), shifting the boronate/boronic-acid equilibrium toward the boronate form at less basic pH.

Further Reading

Choosing Your Boron Source for Suzuki–Miyaura Coupling.

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