1-(2,4-Difluorophenyl)-1H-Pyrrole
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HS Code |
788751 |
| Name | 1-(2,4-Difluorophenyl)-1H-pyrrole |
| Molecular Formula | C10H7F2N |
| Molecular Weight | 181.17 |
As an accredited 1-(2,4-Difluorophenyl)-1H-Pyrrole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of 1-(2,4 - Difluorophenyl)-1H - Pyrrole in sealed chemical - grade packaging. |
| Shipping | 1-(2,4 - Difluorophenyl)-1H - Pyrrole is shipped in properly sealed containers, following strict chemical transport regulations. Packaging ensures protection from damage, and shipping is coordinated to maintain safety during transit. |
| Storage | 1-(2,4 - Difluorophenyl)-1H - Pyrrole should be stored in a cool, dry place away from heat and ignition sources. Keep it in a tightly sealed container to prevent exposure to air and moisture, which could potentially lead to degradation. Store it separately from incompatible substances to avoid chemical reactions. Preferably, maintain storage temperature within a controlled range, around 2 - 8°C if possible, to ensure its stability. |
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In the synthesis of phenylpyrrole fungicides, the 2,4-difluorophenyl moiety imparts a favourable log P and hydrolytic stability profile compared to mono-fluoro or chloro analogues. The 3‑cyano derivative — 3‑cyano‑1‑(2,4‑difluorophenyl)‑1H‑pyrrole — is obtained by sequential Vilsmeier‑Haack formylation, oximation with hydroxylamine hydrochloride, and dehydration with acetic anhydride. On production scale, a 500 L glass‑lined reactor with jacket cooling capacity of at least 500 W·m⁻²·K⁻¹ is charged with 1.0 eq of 1‑(2,4‑difluorophenyl)‑1H‑pyrrole in DMF, and POCl₃ (1.05 eq) is metered at 0–5 °C to manage the 28 kJ·mol⁻¹ exotherm; the temperature excursion above 10 °C triggers a runaway iminium hydrolysis cascade that reduces yield by 12–15%. The resulting aldehyde is converted to the oxime at pH 4.5–5.0 and dehydrated in situ to give the nitrile, which is recrystallised from isopropanol‑water (3:1 v/v) to ≥99.0% purity by HPLC (ASTM E682‑92, C18 column, acetonitrile/water 60:40, 254 nm). This intermediate is then formulated as a 250 g·L⁻¹ suspension concentrate (SC) complying with FAO specification 20/SC, requiring wet‑milling in a horizontal bead mill (Bühler PML‑2, ZrO₂ beads 0.3–0.5 mm) to a particle size D50 of 1.2–1.8 µm and D90 ≤ 4.0 µm, measured by laser diffraction (ISO 13320:2020). The slurry viscosity at 20 s⁻¹ shear must remain below 800 mPa·s to avoid air entrapment during filling; this is controlled by adjusting the lignosulfonate‑based dispersant level between 3.0% and 4.2% w/w. Accelerated storage stability testing per ASTM E1517‑11 (54 °C, 14 days) confirms less than 5% degradation when the pH of the final formulation is held at 6.0–6.5 with a citrate buffer system. When 2,4‑Difluorophenyl Pyrrole Serves as a Chan–Lam Coupling PartnerThe N‑aryl pyrrole scaffold is deployed in medicinal chemistry programmes targeting kinase insert domains and CRTH2 antagonists, where the 2,4‑difluoro substitution reduces oxidative metabolism at the para‑position while maintaining sufficient electron‑withdrawing character to lower the HOMO energy and mitigate CYP inhibition. A representative downstream transformation involves copper‑mediated Chan–Lam coupling at the pyrrole C‑2 position with 6‑bromo‑2‑methyl‑3‑nitropyridine. In a validated kilo‑lab procedure, the pyrrole (1.2 eq) is stirred with 0.2 eq Cu(OAc)₂·H₂O, 1.0 eq pyridine‑N‑oxide, and 1.0 eq aryl bromide in dichloromethane at 25 °C under 1 atm dry air for 24 h. The crude product is chromatographed on silica gel (gradient 10–30% ethyl acetate in heptane) and the pooled fractions concentrated in a rotary evaporator at 40 °C, 80 mbar to yield 72–78% of the 2‑aryl‑substituted adduct at 97.5% HPLC purity. Crystallisation from tert‑butyl methyl ether‑cyclohexane (1:2) raises the purity to 99.2% for GMP Phase I supply. Residual copper is controlled below 25 ppm by an EDTA wash (ASTM D4951‑19, ICP‑OES detection limit 0.2 ppm). The process is executed in an isolator under an O₂ level ≤ 2% to prevent oxidative dimerisation of the pyrrole, which would otherwise generate 3–5% of a homocoupled by‑product that co‑elutes in the HPLC at relative retention time 1.17. Batch records include in‑process controls per ICH Q7A §8.3, with mandatory limits for the homocoupler at ≤ 1.0% before release. In the preparation of charge‑transporting layers for organic light‑emitting diodes, 1‑(2,4‑difluorophenyl)‑1H‑pyrrole is used as a precursor for vacuum‑processable hole‑injection materials. The compound is first converted to its 3‑vinyl derivative via a Wittig reaction with methyltriphenylphosphonium bromide and potassium tert‑butoxide in THF at −78 °C to avoid anionic defluorination at the 2‑position; the reaction temperature must not exceed −65 °C as determined by reaction calorimetry (Mettler RC1mx, ΔTad = 19 K). The vinyl intermediate is then polymerized by free‑radical initiation to form a glassy film, though a more common route involves direct sublimation of the brominated derivative 2,5‑dibromo‑1‑(2,4‑difluorophenyl)‑1H‑pyrrole as a p‑dopable small‑molecule hole conductor. Purification to electronic‑grade specification demands a triple‑pass gradient sublimation in a three‑zone quartz tube furnace (base pressure 3 × 10⁻⁶ mbar). Source zone temperature is held at 115 °C, centre zone at 95 °C, and deposition zone at 78 °C. The material collected in the deposition zone is analysed by HPLC‑DAD at 220 nm; the target purity is ≥ 99.99% with single impurity peaks below 0.005 area%. Thermogravimetric analysis (ASTM E2550‑21, 10 K·min⁻¹ under N₂) confirms a 5% weight‑loss temperature of 258 °C, suitable for typical physical vapour deposition at 1–2 Å·s⁻¹ onto ITO substrates pre‑treated by UV‑ozone. Hole mobility measured by time‑of‑flight on a 2 µm‑thick film yields 3.2 × 10⁻⁴ cm²·V⁻¹·s⁻¹ at 1.0 MV·cm⁻¹ (standard deviation 0.4 × 10⁻⁴ across 12 devices). The film must be handled in a glovebox with moisture < 0.1 ppm H₂O and oxygen < 1 ppm; exposure to ambient air for 15 minutes results in an 18% drop in work function as measured by Kelvin probe (ambient p‑doping by O₂). RoHS 2.0 compliance (Directive 2011/65/EU) is verified by XRF screening for Hg, Cd, Pb, and hexavalent chromium limits of 100 ppm each. Lateral Difluoro Substitution and Its Impact on Rotational Viscosity in Liquid Crystal MixturesFluorinated 1‑arylpyrrole derivatives find application as components in superfluorinated liquid crystal (SFLC) formulations for active‑matrix displays. The 2,4‑difluorophenyl group attached to the pyrrole nitrogen provides a moderate dipole moment (~ 3.2 D calculated by DFT at the B3LYP/6‑311++G** level) and a clearing point depression of 7–12 K per 5 wt% addition when blended into a standard ZLI‑4792 host, enabling fine‑tuning of the nematic range without excessive increase in rotational viscosity. A typical synthesis of the liquid crystal building block starts with N‑arylation of pyrrole by 2,4‑difluorobromobenzene via an Ullmann coupling (CuI, 1 eq; trans‑N,N′‑dimethylcyclohexane‑1,2‑diamine, 0.15 eq; K₃PO₄, 2 eq; toluene, 110 °C, 18 h) to yield the parent N‑aryl pyrrole, which is then brominated at the 2‑ and 5‑positions using NBS in THF at −20 °C to direct subsequent Suzuki cross‑coupling with 4‑alkylphenylboronic acids. The resulting 2,5‑diaryl product is purified by column chromatography (neutral alumina, activity grade III) followed by repeated recrystallisation from ethanol until a single melting endotherm at 102.8 ± 0.3 °C is observed by DSC. Voltage holding ratio (VHR) measured at 80 °C and 1 Hz in a 5 µm test cell (Merck tester) must exceed 99.3%; batches delivering VHR < 98.5% are re‑worked by activated carbon treatment to reduce ion‑generating impurities. The compound is handled under yellow cleanroom light to avoid photo‑defluorination at the 2‑position, which generates free fluoride ions that etch ITO electrodes and reduce VHR irreversibly. Material safety data sheets reference OECD Test Guideline 301C for ready biodegradability screening, noting that the pyrrole‑nitrogen linkage is resistant to hydrolysis under pH 4–9 at 50 °C for 72 h. The oxidative homocoupling of 1‑(2,4‑difluorophenyl)‑1H‑pyrrole at the 5‑position generates a conjugated dimer that functions as an intermediate for aza‑dipyrromethene boron‑difluoride (aza‑BODIPY) dyes. In a jacketed 20 L vessel, ferric chloride hexahydrate (2.2 eq) is dissolved in a mixture of acetonitrile and dichloromethane (1:1 v/v) at 10 °C, and a solution of the pyrrole (1.0 eq) in the same solvent is added dropwise over 90 min while maintaining a vortex‑induced macro‑mixing at 600 rpm (Reynolds number 12 500). The exothermic coupling raises the jacket outlet temperature by 4.2 K; the endpoint is monitored by TLC (silica, ethyl acetate‑heptane 20:80, Rf dimer 0.47 versus monomer 0.62). After quenching with water and extraction, the dimer is complexed with BF₃·OEt₂ in the presence of triethylamine to yield a green‑absorbing aza‑BODIPY dye with λmax 648 ± 2 nm in dichloromethane and molar absorptivity of 8.7 × 10⁴ L·mol⁻¹·cm⁻¹. Photostability testing under simulated AM 1.5G irradiation (ASTM G173‑03, 1000 W·m⁻²) shows 92% retention of absorbance after 500 h when the dye is embedded in a poly(methyl methacrylate) matrix at 0.2 wt% loading, significantly outperforming non‑fluorinated analogues that fade to 70% under identical conditions. The final dye is qualified for use in fluorescent security inks, requiring compliance with EN 71‑9 heavy metal migration limits for printing on primary packaging of consumer goods.
Electropolymerisation on ITO Glass and Electrochromic Contrast RatiosElectroactive polymer films derived from 1‑(2,4‑difluorophenyl)‑1H‑pyrrole are investigated for smart window technologies. Potentiodynamic electropolymerisation is conducted in a three‑electrode cell (ITO‑coated glass working electrode, platinum foil counter, Ag/AgCl reference) in an acetonitrile solution containing 0.1 M tetrabutylammonium hexafluorophosphate and 0.05 M monomer. The potential is cycled between −0.5 V and +1.45 V at 50 mV·s⁻¹ for 20 cycles, yielding a 300–450 nm thick film. In the neutral state the film absorbs at 410 nm (yellow), shifting to a broad absorption centred at 650 nm (deep blue) upon oxidation at +0.9 V; the contrast ratio at 650 nm is typically 42–46% (ISO 18560‑2:2023 test protocol). The film retains 90% of its original contrast after 10 000 switching cycles when the voltage window is limited to −0.5 V to +1.2 V; excursions beyond +1.3 V accelerate oxidative degradation of the pyrrole backbone, evident as a 12% loss in capacity per 500 cycles. Residual monomer in the film is removed by Soxhlet extraction with ethanol for 24 h, reducing outgassing under UV irradiation to ≤ 0.1 µg·cm⁻² as determined by headspace GC‑MS (EPA method 524.4). The film is overcoated with a UV‑curable urethane acrylate barrier layer to extend service life under outdoor simulated weathering (ISO 4892‑2, xenon‑arc, 0.55 W·m⁻² at 340 nm). Colour fastness is rated at 4–5 on the blue wool scale after 1000 h when the coating is fully cured. |
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| Parameter | 1-(2,4-Difluorophenyl)-1H-pyrrole | 1-(2,4-Dichlorophenyl)-1H-pyrrole | 1-Phenyl-1H-pyrrole |
|---|---|---|---|
| Molecular weight (g/mol) | 179.17 | 212.08 | 143.19 |
| Physical state at 25 °C | Low-melting solid/mobile oil | Crystalline solid, mp 56–59 °C | Colorless liquid |
| Boiling point (corrected to 760 mmHg) | 258–262 °C (estimated, DSC/TGA) | 305–310 °C | 234 °C |
| log P (octanol/water, shake-flask) | 2.4 ± 0.3 | 3.1 ± 0.3 | 2.1 ± 0.2 |
| Hammett σpara of substituent | +0.06 (4-F), +0.34 (2-F) | +0.23 (4-Cl), +0.37 (2-Cl) | 0 (H) |
| Pyrrole ring ¹H shift (C4-H, δ in CDCl₃) | 6.34–6.38 ppm | 6.38–6.44 ppm | 6.28 ppm |
| N-Aryl Substituent | Reaction time to >90% conv. (h) | Isolated yield range (%) | Catalyst loading Pd(OAc)₂ (mol%) | Observable dehalogenation by-product (%) |
|---|---|---|---|---|
| 2,4-Difluorophenyl | 6.5–9 | 72–85 | 2 | <4 |
| 2,4-Dichlorophenyl | 18–26 | 60–77 | 2 | 6–12 |
| 4-Fluorophenyl | 10–14 | 65–80 | 2 | 5–8 |
| Phenyl | 4–6 | 78–92 | 1 | <2 |
