2,5-Dibromophenylboronic Acid | CAS 1008106-93-1 | ≥97%

2,5-Dibromophenylboronic Acid ((2,5-Dibromophenyl)boronic Acid, 2,5-Dibromobenzeneboronic Acid) is a trifunctional arylboronic acid building block combining arylboronic-acid reactivity with two positionally and electronically non-equivalent aryl bromide handles on a single phenylene unit.

The product may contain small amounts of the cyclic anhydride 2,5-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 C2 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 the initial coupling at the boronic acid position under conditions that preserve the Ar–Br bonds, the two remaining C–Br bonds at C2 and C5 are available for sequential Pd-catalysed transformations (Suzuki, Stille, Negishi, Sonogashira, Heck, Buchwald–Hartwig amination, Miyaura borylation), enabling the construction of unsymmetrically trisubstituted phenylene cores from a single building block.
• 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.
• Suzuki polycondensation (SPC) monomer logic for conjugated polyarylene backbones: class-level dibromoarene chemistry. The C2/C5 dibromo pattern is 1,4-related and therefore analogous to dibromoarene monomers used in AA/BB-type Suzuki polycondensation with diboronic acid or diboronate partners under Pd catalysis to produce conjugated polyarylene chains. Because this molecule also contains a boronic acid at C1, use as a side-chain, end-group, or branching handle requires suitable protection, stoichiometric control, or deliberately designed polymerisation conditions to avoid competing participation of the C1 boronate in the polymerisation step. Conjugated polymers prepared by Suzuki–Miyaura-type polymerisation are established materials for OLEDs, OFETs, and related organic electronic devices.
• Conversion to the corresponding aryltrifluoroborate: class-level arylboronic-acid chemistry. Treatment with KHF2 in aqueous-methanolic conditions converts the boronic acid to the bench-stable, 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 2,5-dibromophenyl group where the substrate is compatible.
• 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-2,5-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 2,5-dibromophenol.
• Multistep building block for trisubstituted arene cores: the compact trifunctional architecture (one B–OH, two C–Br) on a single phenylene unit makes this compound a starting material for sequential functionalisation strategies in the assembly of asymmetrically substituted arenes used as advanced intermediates.

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.