4-Trifluoromethoxyphenylboronic Acid | CAS 139301-27-2 | ≥98%

4-(Trifluoromethoxy)phenylboronic acid (4-(trifluoromethoxy)benzeneboronic acid) is a fluorinated arylboronic acid bearing the trifluoromethoxy (OCF₃) group at the para position. The OCF₃ substituent is a moderately electron-withdrawing, highly lipophilic fluorinated motif: its inductive electron-withdrawal is partly attenuated by oxygen lone-pair donation relative to CF₃, and para-OCF₃ phenylboronic acid is measurably less acidic than the corresponding para-CF₃ analogue. This electronic and lipophilic profile makes the 4-(trifluoromethoxy)phenyl group a useful substituent for medicinal-chemistry, agrochemical, and fluorinated-materials research.

The product may contain small amounts of the cyclic anhydride 4-(trifluoromethoxy)phenylboroxine; under aqueous or basic coupling conditions the two forms re-equilibrate and the impact on yield is minor.

Applications and Reactions

• Suzuki–Miyaura coupling: couples with aryl, heteroaryl, and alkenyl halides or pseudohalides under Pd catalysis to install the 4-(trifluoromethoxy)phenyl fragment onto biaryl, heterobiaryl, and styrenyl scaffolds.
• Boronate–water equilibrium and acidity profile: the para-OCF₃ substituent gives pKa values of 8.11 ± 0.04 (spectrophotometric) and 8.03 ± 0.07 (potentiometric), roughly 0.7 units below the parent phenylboronic acid (pKa ≈ 8.8) but less acidic than the 4-trifluoromethyl analogue (pKa 7.82 / 7.90). The narrower acidity gap relative to CF₃ reflects partial oxygen lone-pair donation attenuating the inductive effect of OCF₃. This compound-specific acidity profile is useful when selecting base, pH window, and counter-ion for Suzuki–Miyaura, Chan–Lam, or diol-recognition workflows involving boronic-acid/boronate speciation.
• Liquid crystal building block: Suzuki–Miyaura coupling via the corresponding 1,3,2-dioxaborinane boronate ester, or related protected boronate forms such as the pinacol ester, installs the 4-(trifluoromethoxy)phenyl fragment into biphenyl, ethynyl-biphenyl, and ester-linked rod-like cores used as mesogenic units in fluorinated liquid-crystal materials. Reported IR-oriented liquid-crystal studies using 4-(trifluoromethoxy)phenyl boronate intermediates evaluate mesomorphic behaviour, phase-transition temperatures, refractive indices, birefringence, and mid-wave infrared spectral properties, making this motif relevant to rod-like liquid-crystal materials designed for infrared-region applications.
• Perovskite solar cell interface modifier: investigated as a fluorinated phenylboronic-acid interfacial modifier at the perovskite/C₆₀ interface in inverted (CsFAMA)Pb(IBr)₃ perovskite solar cells, alongside its 4-trifluoromethyl analogue. The reported study describes that phenylboronic-acid modifiers of this class can passivate interfacial defects, suppress non-radiative recombination, enhance charge extraction, and reduce trap-state density; the 4-trifluoromethyl analogue showed stronger device-level performance than the 4-(trifluoromethoxy) analogue in the reported comparison.
• Chan–Lam coupling: class-level arylboronic-acid chemistry. The boronic acid can serve as the aryl donor in copper-mediated C–N, C–O, and C–S bond formation under aerobic conditions, transferring the 4-(trifluoromethoxy)phenyl group to suitable amines, anilines, amides, phenols, alcohols, or thiols. Reaction rates and selectivity depend on the copper source, ligand, base, solvent, and nucleophile class.
• Petasis borono-Mannich reaction: class-level arylboronic-acid chemistry. Arylboronic acids can act as aryl donors in three-component reactions with an amine and an aldehyde, glyoxylic acid, or α-hydroxy aldehyde partner to give arylated amines, α-aryl glycine derivatives, or β-amino alcohol scaffolds.
• Protodeboronation and condition sensitivity: class-level arylboronic-acid chemistry. Arylboronic-acid stability under aqueous-basic coupling conditions is substituent-, pH-, base-, concentration-, and temperature-dependent, and pH-controlled boronic-acid/boronate speciation can influence decomposition pathways. For 4-(trifluoromethoxy)phenylboronic acid, whose pKa is approximately 8.0–8.1, prolonged exposure to warm aqueous-basic conditions should be managed by appropriate base choice, concentration, temperature, and reaction time; slow-release boron formats can be considered when extended coupling conditions are required.
• Protected boronate ester forms: the corresponding pinacol ester (4,4,5,5-tetramethyl-2-[4-(trifluoromethoxy)phenyl]-1,3,2-dioxaborolane, CAS 474709-28-9) is commercially documented and provides a protected boronate form for handling and Suzuki–Miyaura coupling workflows. Slow-release boron formats including MIDA boronates and potassium organotrifluoroborates are class-level protection strategies that can improve shelf stability and enable controlled-release coupling protocols; preparation of OCF₃ variants of these formats should be confirmed against substrate-specific procedures when required.

Further Reading

For comprehensive protocols on boronic acids, esters, protodeboronation, boroxine content, and reagent selection, refer to NorrChemica's Lab Journal guide: Choosing Your Boron Source for Suzuki–Miyaura Coupling.