Using Arylboronic Ester T692847 in Suzuki Coupling Reactions
Using Arylboronic Ester T692847 in Suzuki Coupling Reactions
4,4,5,5-Tetramethyl-2-(4-(2,2,2-trifluoroethoxy)phenyl)-1,3,2-dioxaborolane is a fluorine-containing arylboronic acid pinacol ester that serves as a versatile electrophilic-boron building block for palladium-catalyzed Suzuki–Miyaura cross-coupling reactions and related transformations in medicinal and synthetic chemistry.
- Chemical Name
- 4,4,5,5-Tetramethyl-2-(4-(2,2,2-trifluoroethoxy)phenyl)-1,3,2-dioxaborolane
- SKU
- T692847
- Compound Class
- Arylboronic acid pinacol ester (Aryl Bpin)
- Key Functional Groups
- Pinacol boronate ester; 2,2,2-trifluoroethoxy substituent on para-phenyl
- Primary Application
- Suzuki–Miyaura cross-coupling partner; fluorinated arene synthesis
- Storage Recommendation
- Store under inert atmosphere (N₂ or Ar), cool and dry, away from moisture
Chemical Identity and Structure
4,4,5,5-Tetramethyl-2-(4-(2,2,2-trifluoroethoxy)phenyl)-1,3,2-dioxaborolane (SKU: T692847) belongs to the class of arylboronic acid pinacol esters (Bpin), in which the boron atom is protected as a cyclic ester with pinacol (2,3-dimethyl-2,3-butanediol). The phenyl ring carries a para-trifluoroethoxy (–OCH₂CF₃) substituent, introducing a strongly electron-withdrawing, metabolically robust fluorinated ether group onto the aromatic system.
The pinacol ester motif confers improved air- and moisture-stability compared with the corresponding free boronic acid, while still being readily hydrolyzed under standard Suzuki coupling aqueous-base conditions to generate the reactive boronic acid in situ. The –OCH₂CF₃ group is widely used in medicinal chemistry to modulate lipophilicity, improve membrane permeability, and enhance metabolic stability relative to simple methoxy or ethoxy analogues.
Handling, Storage, and Safety Guidelines
Personal Protective Equipment (PPE): Wear appropriate laboratory PPE at all times, including nitrile gloves, safety glasses or goggles, and a laboratory coat. Work in a well-ventilated fume hood when weighing or transferring the compound.
Storage: Store T692847 under an inert atmosphere (nitrogen or argon) in a tightly sealed container, in a cool, dry location away from light and moisture. Boronic esters can slowly hydrolyze on prolonged exposure to atmospheric moisture; therefore, minimize the duration of exposure during weighing operations and reseal containers promptly.
Stability: As a pinacol boronate ester, T692847 is more bench-stable than its corresponding boronic acid. Nevertheless, it is advisable to assess purity by 11B NMR or HPLC prior to use in sensitive reactions, particularly if the material has been stored for an extended period after opening.
Disposal: Dispose of waste material in accordance with applicable local, regional, and national regulations for organoboron compounds. Consult the Safety Data Sheet (SDS) provided with the product for complete hazard and disposal information.
Protocol: Suzuki–Miyaura Cross-Coupling
The following is a general guideline for performing a Suzuki–Miyaura cross-coupling reaction using T692847 as the arylboronic ester coupling partner. Researchers should optimize conditions for their specific substrate and scale.
- Setup: Charge a dry, inert-atmosphere Schlenk flask or sealed vial with the aryl halide substrate (1.0 equiv), T692847 (1.1–1.5 equiv), palladium catalyst (e.g., Pd(PPh₃)₄ or Pd(dppf)Cl₂, 1–5 mol%), and base (e.g., K₂CO₃, Cs₂CO₃, or K₃PO₄, 2–3 equiv).
- Solvent: Use a degassed mixed solvent system such as DMF/H₂O (4:1), dioxane/H₂O (4:1), or toluene/EtOH/H₂O (2:1:1). Degassing is critical to prevent catalyst oxidation; perform three freeze–pump–thaw cycles or sparging with inert gas for at least 20 minutes.
- Reaction: Stir the mixture at 80–100 °C under inert atmosphere until full conversion is observed by TLC or LC-MS (typically 2–16 h, substrate-dependent).
- Workup: Cool to room temperature. Dilute with ethyl acetate, wash with water and brine, dry over MgSO₄ or Na₂SO₄, filter, and concentrate under reduced pressure.
- Purification: Purify the crude product by flash column chromatography (silica gel) or recrystallization as appropriate. Verify the fluorinated biaryl product by ¹H NMR, ¹⁹F NMR, and HRMS.
Note: The 2,2,2-trifluoroethoxy group is stable under these basic aqueous conditions and does not require special protection.
Applications in Medicinal and Synthetic Chemistry
T692847 is a valuable building block in the synthesis of fluorinated biaryl compounds, which appear frequently in drug discovery programs. The trifluoroethoxy pharmacophore is present in several approved pharmaceuticals and clinical candidates, where it imparts desirable physicochemical properties including reduced basicity, improved metabolic stability at the aromatic ring, and modulated log P values compared with non-fluorinated analogues.
Typical applications include:
- Drug discovery: Introducing a 4-(2,2,2-trifluoroethoxy)phenyl fragment into lead compounds to improve ADMET properties.
- Materials science: Synthesis of fluorinated liquid crystals or organic semiconductors where the CF₃-containing ether provides specific dielectric or electronic properties.
- Methodology studies: Benchmarking new palladium or nickel catalysts and ligand systems in cross-coupling reaction development.
The modular nature of Suzuki–Miyaura coupling means T692847 can be paired with a broad range of aryl, heteroaryl, vinyl, and alkyl halide or pseudohalide partners, enabling rapid library synthesis.
Quality Control and Analytical Characterization
To ensure reproducible reaction outcomes, verify the purity and integrity of T692847 before use:
- ¹H NMR: Confirm the aromatic proton pattern (para-substituted phenyl, AA'BB' system), pinacol methyl singlet (~1.33 ppm), and the characteristic OCH₂CF₃ quartet (~4.3 ppm).
- ¹¹B NMR: A single peak near δ 30 ppm is diagnostic for a tricoordinate pinacol boronate ester; absence of a peak near δ 0–5 ppm rules out significant boronic acid contamination.
- ¹⁹F NMR: The –OCH₂CF₃ group appears as a triplet near δ –74 ppm (referenced to CFCl₃); a single clean signal confirms integrity of the trifluoroethoxy group.
- HPLC: Reverse-phase HPLC (C18, UV 254 nm) can assess chemical purity; aim for ≥95% purity for synthetic applications.
- HRMS: High-resolution mass spectrometry (ESI or APCI) should confirm the molecular formula; note that boronic esters can partially hydrolyze to the free boronic acid under ESI conditions, so both species may be observed.
Frequently asked questions
What palladium catalyst is recommended for Suzuki coupling with T692847?
Commonly used catalysts include Pd(PPh₃)₄ (air-free conditions) and Pd(dppf)Cl₂ (for more challenging substrates). The optimal choice depends on the coupling partner; electron-rich aryl chlorides may require more active second- or third-generation palladium precatalysts such as Pd-PEPPSI or SPhos Pd G3.
Is the 2,2,2-trifluoroethoxy group stable under Suzuki coupling conditions?
Yes. The –OCH₂CF₃ group is a simple aliphatic ether and is chemically inert under the mildly basic aqueous conditions typically employed in Suzuki–Miyaura coupling (K₂CO₃ or Cs₂CO₃ in water/organic solvent at 80–100 °C). No special protecting-group strategy is required for this substituent.
How should T692847 be stored to prevent degradation?
Store T692847 sealed under an inert gas (N₂ or Ar) in a cool, dry location. Although the pinacol ester is more moisture-resistant than the free boronic acid, prolonged exposure to atmospheric humidity or heat can cause slow hydrolysis or protodeboronation. Check purity by ¹¹B NMR before use if the container has been opened multiple times.
Can T692847 be used in reactions other than Suzuki coupling?
Yes. Arylboronic pinacol esters are versatile intermediates. T692847 can participate in Chan–Lam coupling (C–N, C–O bond formation with Cu catalysis), Matteson homologation, oxidation to the corresponding phenol, and various transition-metal-free C–B functionalization reactions. The Bpin group can also be converted to a boronic acid by hydrolysis or to a trifluoroborate salt by treatment with KHF₂.
What analytical method confirms successful Suzuki coupling using this boronate?
Successful coupling can be confirmed by the disappearance of the Bpin ¹¹B NMR signal (~30 ppm) and the appearance of the biaryl product by ¹H NMR, ¹⁹F NMR (retention of the –OCH₂CF₃ triplet near –74 ppm), and HRMS. LC-MS monitoring during the reaction is also highly recommended for efficient optimization.
References
- Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chem. Rev. 1995, 95, 2457–2483. doi:10.1021/cr00039a007
- Hall, D. G. (Ed.) Boronic Acids: Preparation and Applications in Organic Synthesis, Medicine and Materials, 2nd ed.; Wiley-VCH: Weinheim, 2011.
- Gillis, E. P.; Burke, M. D. Multistep Synthesis of Complex Boronic Acids from Simple MIDA Boronates. J. Am. Chem. Soc. 2007, 129, 6716–6717. doi:10.1021/ja070394d
- Meanwell, N. A. Synopsis of some recent tactical application of bioisosteres in drug design. J. Med. Chem. 2011, 54, 2529–2591. doi:10.1021/jm1013898
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