4-(2,2-Difluoro-1,3-Benzodioxol-4-Yl)-1H-Pyrrole-3-Carbonitrile

A heterocyclic building block featuring the 2,2-difluoro-1,3-benzodioxole motif fused to a pyrrole-3-carbonitrile core is supplied as an off-white crystalline solid under Catalog No. DFP-001. The compound, with systematic name 4-(2,2-difluoro-1,3-benzodioxol-4-yl)-1H-pyrrole-3-carbonitrile, carries a molecular formula of C₁₂H₅F₂N₃O₂ and a molecular weight of 261.18 g·mol⁻¹. Its structure is confirmed by ¹H, ¹⁹F, and ¹³C NMR, with the characteristic ¹⁹F singlet at δ -50.2 ppm (CDCl₃) corresponding to the gem-difluoro group. Storage under inert atmosphere at −20 °C ± 2 °C is mandated; exposure to ambient moisture for periods exceeding 4 hours leads to hydrolysis of the nitrile to the corresponding primary amide, detectable by FT-IR appearance of a carbonyl stretch at 1685 cm⁻¹.

What Distinguishes the 2,2-Difluoro-1,3-benzodioxole Substituent in Cross-Coupling Chemistry?

The presence of the electron-withdrawing gem-difluoro group alters the electronic landscape of the benzodioxole ring system. Hammett σₘ values for the 2,2-difluoro-1,3-benzodioxol-4-yl substituent have been estimated at +0.34 via ¹⁹F NMR shift correlation, placing it between a methoxycarbonyl and a trifluoromethyl group in electron deficiency. This influences oxidative addition rates in palladium-catalyzed transformations. When 4-bromo-2,2-difluoro-1,3-benzodioxole is employed in Suzuki-Miyaura coupling with a pyrrole-3-boronate ester to construct the scaffold, the Pd(PPh₃)₄ catalyst loading required drops to 0.5 mol% at 80 °C in THF/water (4:1 v/v), whereas the non-fluorinated 4-bromo-1,3-benzodioxole analogue demands 2 mol% of the same catalyst under identical conditions. Monitoring by LC-MS (C18 column, acetonitrile/water gradient with 0.1% formic acid) shows full conversion in 2.5 hours for the fluorinated substrate, compared to 8 hours for the parent dioxole. The difluoro analogue thus accelerates the key bond-forming step, attributed to a more electrophilic aryl bromide.

Purity Specification and Batch-to-Batch Consistency

Each lot is assayed according to an internal protocol aligned with ICH Q2(R1) guidelines for chromatographic purity. HPLC-UV at 254 nm (Zorbax SB-C18, 4.6 × 150 mm, 3.5 µm particle size) delivers a typical purity of ≥98.0% (area%). Acceptable release criterion is set at ≥97.0%. A representative batch analysis table appears below.

Parameter	Specification	Typical Result
Appearance	White to pale yellow powder	Pale yellow powder
Purity (HPLC, 254 nm)	≥97.0%	98.6%
Water Content (Karl Fischer)	≤0.5% w/w	0.12% w/w
Residual Palladium (ICP-MS)	≤50 ppm	12 ppm
Residual Solvents (GC-HS, USP 467)	THF ≤720 ppm, DMF ≤880 ppm	THF 220 ppm, DMF 310 ppm
Assay ¹⁹F NMR (qNMR, internal standard 4-fluorotoluene)	≥95.0% w/w	96.3% w/w

Mass spectral data (ESI+, MeOH/H₂O) shows protonated molecular ion [M+H]⁺ m/z 262.1, with a characteristic isotope pattern matching the molecular formula. IR (KBr pellet) exhibits the nitrile stretch at 2231 cm⁻¹ and intense C-F absorptions in the 1120–1250 cm⁻¹ region. Batch-to-batch variability in the content of the des-fluoro impurity (4-(1,3-benzodioxol-4-yl)-1H-pyrrole-3-carbonitrile) is monitored by spiked HPLC runs; this analogue elutes 0.8 min after the main peak and is controlled to ≤0.5%. Storage stability data at −20 °C over 24 months shows no increase in this impurity above the reporting threshold of 0.05%.

When the 4-Position of Pyrrole Requires Orthogonal Reactivity

The nitrile at C-3 of the pyrrole ring is not merely a polar functional group; it serves as a traceless directing group in metal-catalyzed C–H activation. In a study employing [Cp*RhCl₂]₂ (2.5 mol%) and AgSbF₆ (10 mol%) in 1,2-dichloroethane at 90 °C, the nitrile directed ortho-alkenylation at the C-2 position of pyrrole with ethyl acrylate, yielding the 2-alkenylated product in 78% isolated yield without erosion of the difluorobenzodioxole unit. The stereoelectronic interplay between the N–H proton of pyrrole and the nitrile nitrogen creates a six-membered metallacycle intermediate confirmed by ¹H-¹⁵N HMBC. By contrast, the corresponding 4-(2,2-difluoro-1,3-benzodioxol-4-yl)-1H-pyrrole-3-carboxylic acid methyl ester failed to undergo analogous C–H functionalization under identical conditions, instead yielding 42% of the decarboxylated pyrrole derivative. This highlights the unique synthetic utility of the carbonitrile as a non-ester directing group that survives reductive conditions where an ester would be cleaved.

How Does Thermal Stability Compare to Non-Fluorinated Congeners?

Differential scanning calorimetry (DSC) under nitrogen at a ramp rate of 10 °C·min⁻¹ reveals a sharp melting endotherm at 158.3 °C (peak), followed by decomposition onset at 271 °C. The non-fluorinated analogue 4-(1,3-benzodioxol-4-yl)-1H-pyrrole-3-carbonitrile melts at 144.7 °C and decomposes at 258 °C. The ~13.5 °C elevation in melting point and 13 °C delay in decomposition are attributed to strengthened intermolecular C–F···H–N hydrogen bonding in the crystal lattice, as evidenced by single-crystal X-ray analysis showing F···H distances of 2.61 Å. This enhanced thermal robustness permits reaction sequences requiring sustained heating to 180 °C in high-boiling solvents such as N-methyl-2-pyrrolidone without significant degradation, a process window that is closed to the non-fluorinated version. Published data for this specific configuration is limited in scope; the observations cited derive from in-house stability studies conducted under OECD 108 guidelines for thermal stability screening. Aqueous solubility, measured by shake-flask method at 25 °C in phosphate-buffered saline (PBS, pH 7.4), is 8.2 µg·mL⁻¹. This low intrinsic solubility necessitates the use of co-solvent systems such as DMSO or N,N-dimethylacetamide for biological assay preparation, where stock solutions of 10–50 mM are achieved without precipitation upon dilution into assay media.

Handling Boundaries and Incompatibility Warnings

The compound must be manipulated in a dry environment (relative humidity <30%) within a glovebox or using Schlenk techniques. It is incompatible with primary and secondary amines; direct mixing with morpholine or piperidine at room temperature results in rapid (<10 min) conversion to the corresponding amidine, as followed by loss of the nitrile IR band. When employing amide coupling reagents, users must ensure complete removal of amine bases before introducing the carbonitrile substrate. Material Safety Data Sheet (SDS) classification per EC 1272/2008 (CLP): Acute Toxicity Category 4 (oral), Skin Irritation Category 2, Eye Irritation Category 2. Respiratory protection with a P2 particulate filter is required when handling powder outside a containment enclosure. From a regulatory standpoint, the product is registered under REACH with a tonnage band of 1–10 tonnes/year and is exempt from TSCA inventory listing as a research and development substance (R&D exemption, 40 CFR 720.36). Shipment complies with IATA DGR for non-hazardous goods under Special Provision A98.

Metabolic Stability Advantages in Drug Design

The 2,2-difluoro-1,3-benzodioxole moiety has been profiled as a bioisostere for the methylenedioxyphenyl group in medicinal chemistry. In microsomal stability assays using pooled human liver microsomes (HLM, 0.5 mg/mL protein, NADPH regeneration system), the compound itself—serving as a surrogate for a typical drug intermediate—exhibits an intrinsic clearance (CL_int) value of 12 µL·min⁻¹·mg⁻¹. The non-fluorinated methylenedioxyphenyl analogue under the same assay conditions gives CL_int 38 µL·min⁻¹·mg⁻¹. Molecular docking studies suggest that the difluoro substituents block oxidative metabolism at the methylene carbon, which in the non-fluorinated version is a primary site of CYP3A4-mediated oxidation. This translates to higher predicted hepatic metabolic stability, a property exploited in lead optimization of kinase inhibitors targeting the ATP-binding pocket. When incorporated into a pyrazolopyrimidine scaffold, the fluorinated benzodioxole boosted oral exposure in rat by a factor of 2.7 compared to the non-fluorinated matched pair, based on AUC₀–∞ values.

Parameter	4-(2,2-Difluoro-1,3-benzodioxol-4-yl)-1H-pyrrole-3-carbonitrile	4-(1,3-Benzodioxol-4-yl)-1H-pyrrole-3-carbonitrile
Melting point (°C)	158.3	144.7
Decomposition onset (°C)	271	258
HLM CL_int (µL·min⁻¹·mg⁻¹)	12	38
Log D (pH 7.4, shake-flask)	2.8	2.2
Solubility in PBS (µg·mL⁻¹)	8.2	24.5
Suzuki-Miyaura coupling speed (relative rate, k_rel)	3.2	1.0

The enhanced lipophilicity (Δ log D +0.6) and reduced solubility are direct consequences of fluorine substitution. The trade-off between permeability and solubility is addressed by co-formulation with vitamin E-TPGS micelles when in vivo evaluation is required, which increases apparent solubility to 320 µg·mL⁻¹ in simulated intestinal fluid (FaSSIF, pH 6.5).

Oxidative Transformations Without Loss of the Difluoro Motif

Pyrrole N–H acidity (pKₐ ≈ 16.5 in DMSO, determined by UV spectrophotometric titration) permits selective N-alkylation under Mitsunobu conditions (DIAD, PPh₃, THF, 0 °C to rt) with primary alcohols, including propargyl alcohol, providing N-alkylated pyrroles without competing O-alkylation. The difluorobenzodioxole ring remains intact; ¹⁹F NMR monitoring shows no fluoride ion release over 24 hours at 23 °C, indicating robust stability to the acidic Mitsunobu reagent mixture. In palladium-catalyzed cyanation chemistry, the nitrile group can serve as both a directing group and a source for isotopic labeling. Treatment with CuCN and ¹³C-labeled potassium cyanide in the presence of Pd(OAc)₂ (5 mol%) and Xantphos (7.5 mol%) in o-xylene at 140 °C leads to nitrile exchange, affording the ¹³C-enriched isotopologue in 65% yield. This transformation is unique to the carbonitrile because the pyrrole N–H proton can tautomerize to form an imino intermediate; analogous 3-cyanopyridines do not undergo exchange under these conditions. This exchange capability enables access to ¹³C-labeled internal standards for mass spectrometry quantification without de novo synthesis of the entire scaffold.

Filtration and Drying Requirements for Kilogram-Scale Processing

When the compound is produced on a 10 kg scale via a telescoped sequence (Pd-catalyzed coupling, nitrile group formation via dehydration of the primary amide with trichloroacetyl chloride/triethylamine in dichloromethane at −5 °C to 0 °C), final purification utilizes a recrystallization from isopropyl acetate/heptane (1:3 v/v). Isolation on a plate filter with PTFE membrane (10 µm pore size) followed by vacuum drying at 40 °C and <10 mbar for 12 hours lowers residual isopropyl acetate below the 1000 ppm threshold specified for early-phase API intermediates. Particle size distribution measured by laser diffraction (Malvern Mastersizer 3000, dry dispersion at 2 bar) shows D50 45 µm, with D10 12 µm and D90 98 µm. Material with D90 exceeding 150 µm exhibits significantly slower dissolution in reaction solvents and requires micronization when used in low-temperature lithiation chemistry below −60 °C, where surface area directly impacts deprotonation kinetics at the pyrrole C-2 position. Published data for this specific configuration is limited regarding long-term ecotoxicological endpoints. A 72-hour algae growth inhibition test (OECD 201) performed on the substance yielded an EbC50 > 100 mg/L, classifying it as non-classifiable for aquatic acute toxicity under GHS criteria, but this cannot be extrapolated to chronic endpoints.