4-Chlorophenylboronic Acid

Technical Specifications

Product Description & Scientific Applications

4-Chlorophenylboronic Acid (4-chlorobenzeneboronic acid, p-chlorophenylboronic acid) bears a para-chlorine that is moderately electron-withdrawing (σp +0.23), with inductive withdrawal outweighing weak resonance donation, lowering the boronic-acid pKa below that of phenylboronic acid (≈ 8.9). The aryl C–Cl bond is also a useful synthetic handle: after installation of the 4-chlorophenyl unit, it can be retained for later Pd- or Ni-catalysed cross-coupling, Buchwald–Hartwig amination, or related aryl chloride chemistry under suitable conditions. Used as a 4-chlorophenyl building block in medicinal chemistry, agrochemicals, functional molecules, and materials intermediates.

May contain small amounts of the cyclic anhydride 4-chlorophenylboroxine. Under aqueous or basic coupling conditions the two forms re-equilibrate and the impact on yield is minor.

Applications and Reactions

• Suzuki–Miyaura coupling: with aryl, heteroaryl, or alkenyl electrophiles to give 4-chlorophenyl biaryls, heterobiaryls, terphenyls, and styrenyl products. The residual aryl chloride can be retained for later diversification.
• Iterative cross-coupling at the chloride handle: the C–Cl bond in 4-chlorophenyl products can be engaged in later Suzuki–Miyaura, Buchwald–Hartwig, or related Pd/Ni-catalysed reactions when the ligand system and substrate class support aryl chloride activation.
• Chan–Lam coupling: copper-mediated C–N and C–O arylation onto amines, amides, sulfonamides, carbamates, N–H heterocycles, phenols, and selected alcohols.
• Petasis borono-Mannich reaction: three-component coupling with an amine and a carbonyl partner to give α-aryl amines, α-amino acids, or β-amino alcohols bearing the 4-chlorophenyl group, metal-free.
• Pd- and Ru-catalysed direct arylation: aryl source in palladium- and ruthenium-catalysed direct arylation and related C–H functionalisation chemistry.
• Cyclopalladation and tandem Pd chemistry: reported in cyclopalladation, Pd-catalysed arylative cyclisation, and tandem Pd(II)-catalysed oxidative Heck / intramolecular C–H amidation sequences.
• Regioselective arylation and alkynylation: reported in Suzuki–Miyaura and Sonogashira-type cross-coupling sequences where the 4-chlorophenyl unit is part of the arylation/alkynylation design.
• Protected boronate esters: precursor to pinacol (Bpin), neopentyl glycol, and MIDA esters when a more robust 4-chloroaryl-boron building block is required for staged or iterative synthesis.
• Ipso-halodeboronation: to 1-bromo-4-chlorobenzene, 1,4-dichlorobenzene, or 1-chloro-4-iodobenzene under electrophilic halogenation.
• Oxidative hydroxylation: to 4-chlorophenol under aerobic photoredox, peroxide, or copper-catalysed conditions.

Further Reading

Choosing Your Boron Source for Suzuki–Miyaura Coupling.

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