3,5-Dibromophenylboronic Acid CAS 117695-55-3 | ≥98%

3,5-Dibromophenylboronic Acid ((3,5-Dibromophenyl)boronic Acid, 3,5-Dibromobenzeneboronic Acid) is a trifunctional arylboronic acid building block with two electronically equivalent bromide groups that may serve as useful secondary synthetic handles.

The product may contain small amounts of the cyclic anhydride 3,5-dibromophenylboroxine; under aqueous or basic coupling conditions the two forms re-equilibrate and the impact on yield is minor.

Applications and Reactions

• Suzuki–Miyaura coupling: as an arylboronic acid, couples with suitably chosen aryl, heteroaryl, and alkenyl halides or triflates under Pd-catalysed basic conditions to give biaryl, heterobiaryl, and styrene-type products. Because the internal C3 and C5 aryl bromides are themselves potential Pd-oxidative-addition sites, chemoselective coupling at the boronate with retention of both Ar–Br handles is not the automatic outcome of generic Suzuki conditions: it requires deliberately designed conditions (catalyst/ligand choice, base, controlled stoichiometry of the external electrophile, temperature) that favour transmetalation from the boronic acid over oxidative addition into the internal C–Br bonds.
• Sequential cross-coupling on a trifunctional scaffold: after initial coupling at the boronic acid position under conditions that preserve the Ar–Br bonds, the two equivalent C–Br bonds at C3 and C5 are available for further Pd-catalysed transformations (Suzuki, Stille, Negishi, Sonogashira, Heck, Buchwald–Hartwig amination, Miyaura borylation). Because the two bromides are chemically equivalent, mono- versus di-substitution is controlled by stoichiometry of the second electrophile rather than by intrinsic site discrimination, giving access either to 3-substituted 5-bromo or to symmetrically 3,5-disubstituted biaryl intermediates.
• Building block for 1,3,5-trisubstituted benzene cores and C3-symmetric star-shaped scaffolds: after Suzuki coupling at the boronic acid position and subsequent double cross-coupling at the two equivalent Ar–Br positions, this compound gives 1,3,5-trisubstituted benzene cores with a 120° angular disposition of three arms. With three identical Ar groups installed at C1/C3/C5, the product is a C3-symmetric 1,3,5-triarylbenzene, a recurrent core motif in star-shaped π-conjugated oligomers, tripodal ligands, discotic liquid crystals, and extended oligophenylene precursors used in Scholl-type oxidative cyclodehydrogenation approaches to C3-symmetric nanographene and hexabenzocoronene-related architectures.
• AB2-type Suzuki polycondensation to hyperbranched poly(m-phenylene)s: this compound has been reported as an AB2 monomer in Pd-catalysed Suzuki–Miyaura polycondensation, in which the single B(OH)2 "A" function and the two equivalent "B" Ar–Br functions undergo self-condensation to give hyperbranched poly(m-phenylene) architectures. Related AB2 frameworks (e.g. m-terphenyl-derived AB2 monomers under Pd(OAc)2/SPhos catalysis) give higher molecular weights and lower dispersities, consistent with a pseudo-chain-growth pathway involving intramolecular catalyst transfer.
• 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.
• Conversion to the corresponding aryltrifluoroborate: class-level arylboronic-acid chemistry. Treatment with KHF2 in aqueous-methanolic conditions converts the boronic acid to the crystalline potassium aryltrifluoroborate salt, which serves as a bench-stable, hydrolytically robust organoboron coupling partner under conditions where the free boronic acid is prone to protodeboronation, while retaining the aryl bromide substitution pattern.
• Protected boronate derivatives: class-level options including the pinacol (Bpin) ester, MIDA boronate, neopentyl glycol ester, Bdan, and MEA boronate, to be selected case by case depending on the workflow (chromatographic stability, MIDA-type slow-release iterative coupling, handling).
• Chan–Lam-type C–N and C–O coupling: class-level arylboronic-acid chemistry. With Cu(OAc)2 or related Cu(II) systems and an amine, amide, sulfonamide, carbamate, phenol, or selected alcohol partner under mild aerobic conditions, gives the corresponding N-aryl or O-aryl product at the boronic acid carbon, with the two C–Br bonds normally retained.
• 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, including α-aryl glycine and β-amino alcohol scaffolds carrying the 3,5-dibromophenyl group where the substrate is compatible.
• 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 σmeta 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.
• Ipso-halodeboronation: class-level arylboronic-acid chemistry. With NBS, NCS, or NIS, or related halogenating systems, the C–B bond can be converted to C–X to access the corresponding 1-halo-3,5-dibromobenzene framework from this substrate.
• Oxidative ipso-hydroxylation: class-level arylboronic-acid chemistry. With H2O2, oxone, sodium perborate, or copper-/photo-mediated aerobic hydroxylation conditions, the C–B bond can be replaced by C–OH to give 3,5-dibromophenol.
• Multistep building block for 1,3,5-trisubstituted arene cores: the compact trifunctional architecture (one B–OH at C1, two equivalent C–Br at C3/C5) on a single phenylene unit makes this compound a starting material for sequential or convergent functionalisation strategies in the assembly of 1,3,5-trisubstituted arenes with defined three-fold geometry.

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.