4-Bromo-2-nitrophenylboronic Acid: Properties & Lab Guide

4-Bromo-2-nitrophenylboronic acid is an arylboronic acid building block bearing both a bromo substituent and an ortho-nitro group on the phenyl ring, making it a versatile bifunctional reagent widely employed in palladium-catalyzed cross-coupling reactions and medicinal chemistry synthesis.

CAS Number

To be confirmed — see product datasheet (review flag)

Molecular Formula

C6H5BBrNO4

Molecular Weight

Approximately 245.82 g/mol (review flag — verify against CoA)

Appearance

Off-white to pale yellow crystalline powder (typical for arylboronic acids; review flag)

Key Functional Groups

Boronic acid (–B(OH)2), bromo (–Br), nitro (–NO2)

Primary Application

Suzuki–Miyaura and related Pd-catalyzed cross-coupling reactions; medicinal chemistry building block

SKU

B187193

Chemical Identity and Key Properties

4-Bromo-2-nitrophenylboronic acid (SKU B187193) is an arylboronic acid characterised by three distinct functional groups on the benzene ring: a boronic acid group (–B(OH)₂) at the 1-position, a nitro group (–NO₂) at the 2-position (ortho), and a bromine atom at the 4-position (para). This substitution pattern creates an electron-deficient aromatic system, as both the nitro and boronic acid groups are electron-withdrawing.

The compound's bifunctional nature is synthetically significant: the boronic acid moiety participates in Suzuki–Miyaura coupling at carbon C-1, while the aryl bromide at C-4 serves as an electrophilic partner in a second, independent cross-coupling or substitution reaction. The ortho-nitro group can additionally be used as a handle for further functional-group transformations, including reduction to an amine, diazotization, or cyclization reactions.

Physicochemical notes: Arylboronic acids bearing electron-withdrawing substituents typically display higher aqueous solubility than their electron-rich counterparts and are less prone to protodeboronation under mildly acidic conditions. The exact melting point, purity specification, and CAS number should be confirmed against the current Certificate of Analysis (CoA) available from Aladdin Scientific.

Synthetic Applications and Reaction Guidelines

Suzuki–Miyaura Cross-Coupling: The boronic acid group of 4-Bromo-2-nitrophenylboronic acid undergoes palladium-catalyzed Suzuki–Miyaura coupling with aryl or vinyl halides (or pseudohalides) in the presence of a base and a Pd(0) or Pd(II) catalyst. Typical catalysts include Pd(PPh₃)₄, Pd(dppf)Cl₂, or Pd(OAc)₂/SPhos. Bases such as K₂CO₃, Cs₂CO₃, or K₃PO₄ in aqueous-organic solvent mixtures (e.g., DMF/H₂O, dioxane/H₂O) are commonly employed.

Sequential or Orthogonal Functionalization: Because the aryl bromide at C-4 is independent of the boronic acid at C-1, chemists can exploit orthogonal reactivity. In one common strategy, the boronic acid is used in a Suzuki coupling first (forming the biaryl linkage), and the remaining aryl bromide is then engaged in a subsequent cross-coupling (e.g., Buchwald–Hartwig amination, Sonogashira coupling, or a second Suzuki coupling) to build complex molecular architectures.

Nitro Group Utilization: The ortho-nitro group may be selectively reduced to an aniline using catalytic hydrogenation (H₂/Pd-C) or chemical reductants (e.g., Fe/AcOH, SnCl₂). The resulting ortho-aminoaryl intermediate is a versatile precursor to benzimidazoles, benzoxazoles, and other N-heterocycles of pharmaceutical relevance.

Note: Optimal reaction conditions, catalyst loadings, and solvent systems should be established empirically for each specific substrate combination. Consult primary literature for precedent reactions involving structurally similar boronic acids.

Handling, Storage, and Safety Guidelines

General Handling Precautions: As with all arylboronic acids, 4-Bromo-2-nitrophenylboronic acid should be handled in a well-ventilated fume hood. Wear appropriate personal protective equipment (PPE) including chemical-resistant gloves, safety glasses, and a laboratory coat. Avoid generating and inhaling dust. The nitro group confers additional irritancy risk; treat the compound as a potential skin and respiratory irritant until full toxicological data are available from the Safety Data Sheet (SDS).

Storage Conditions: Store the compound in a tightly sealed container under cool, dry conditions, away from light and moisture. Arylboronic acids are susceptible to slow oxidation and anhydride formation (boroxine formation) upon prolonged exposure to ambient humidity. Storage under an inert atmosphere (N₂ or Ar) is recommended for long-term stability. Refer to the product SDS and CoA from Aladdin Scientific for the specific recommended storage temperature.

Stability Considerations: Electron-deficient arylboronic acids are generally more stable toward protodeboronation than electron-rich analogues. However, aqueous solutions should be prepared fresh and used promptly. Avoid strongly acidic or strongly basic conditions during workup, as these can promote boronic acid hydrolysis or decomposition.

Waste Disposal: Dispose of waste containing this compound in accordance with local institutional regulations and applicable environmental legislation. Do not pour down the drain without appropriate treatment.

Quality, Purity, and Procurement Considerations

Purity and Specification: For synthetic and analytical research applications, high purity (typically ≥95% or ≥97% by HPLC or NMR assay) is recommended to ensure reproducible results and to minimise the effect of impurities on catalytic reactions. Palladium-catalyzed cross-couplings are particularly sensitive to catalyst poisons; impurities present in boronic acid reagents can deactivate the catalyst and reduce yields. Always request and review the Certificate of Analysis (CoA) for the specific lot you are using.

Analytical Characterisation: The identity and purity of 4-Bromo-2-nitrophenylboronic acid can be confirmed by ¹H NMR (characteristic aromatic proton signals and broad B–OH resonances), ¹¹B NMR (trigonal boronic acid typically resonates around δ 28–32 ppm), HPLC, and, where appropriate, mass spectrometry.

Ordering Information: 4-Bromo-2-nitrophenylboronic acid is available from Aladdin Scientific under SKU B187193. For current pricing, available pack sizes, and lead times, please visit the Aladdin Scientific product page or contact our customer service team. Bulk quantities may be available upon request.

Frequently asked questions

What is 4-Bromo-2-nitrophenylboronic acid used for?

It is primarily used as a bifunctional building block in palladium-catalyzed Suzuki–Miyaura cross-coupling reactions, where the boronic acid group couples with aryl or vinyl halides. The retained aryl bromide and ortho-nitro group enable sequential functionalization, making it valuable for constructing complex biaryl scaffolds and heterocyclic intermediates in medicinal chemistry and materials science research.

How should 4-Bromo-2-nitrophenylboronic acid be stored to maintain stability?

The compound should be stored in a tightly sealed container in a cool, dry location away from light and moisture. For long-term storage, keeping it under an inert atmosphere such as nitrogen or argon is recommended to prevent slow oxidation and boroxine (anhydride) formation. Always refer to the current Aladdin Scientific Safety Data Sheet and Certificate of Analysis for lot-specific storage instructions.

Can the aryl bromide and boronic acid groups of this compound be reacted independently?

Yes. The aryl bromide at C-4 and the boronic acid at C-1 are chemically orthogonal under appropriate conditions, enabling sequential cross-coupling strategies. For example, the boronic acid can first participate in a Suzuki coupling to install one aryl group, and the remaining aryl bromide can subsequently undergo Buchwald–Hartwig amination, Sonogashira coupling, or another Suzuki coupling, enabling the efficient assembly of complex molecular architectures.

What purity grade is recommended for use in sensitive palladium-catalyzed reactions?

For palladium-catalyzed cross-coupling reactions, a purity of ≥95% (preferably ≥97%) as determined by HPLC or NMR assay is recommended. Even trace impurities in boronic acid substrates can act as catalyst poisons and reduce yields or reproducibility. Always review the lot-specific Certificate of Analysis from Aladdin Scientific before use.

References

1. Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chemical Reviews 1995, 95 (7), 2457–2483. doi:10.1021/cr00039a007
2. Hall, D. G. (Ed.) Boronic Acids: Preparation and Applications in Organic Synthesis, Medicine and Materials, 2nd ed.; Wiley-VCH: Weinheim, 2011.
3. Lennox, A. J. J.; Lloyd-Jones, G. C. Selection of boron reagents for Suzuki–Miyaura coupling. Chemical Society Reviews 2014, 43 (1), 412–443. doi:10.1039/C3CS60197H

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