Pyrrole-2-Carboxylic Acid Ethyl Ester

Product Name Pyrrole-2-Carboxylic Acid Ethyl Ester
Alias Ethyl 1H-pyrrole-2-carboxylate
Einecs 212-593-2
Mininmum Order 1g
Factory Site West Ujimqin Banner, Xilingol League, Inner Mongolia, China
Price Inquiry sales9@bouling-chem.com
Manufacturer Bouling Chemical Co., Limited
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In terms of specification, Pyrrole-2-Carboxylic Acid Ethyl Ester is supplied with ≥98% purity (GC) and a melting range of 39–43°C, making it suitable for use as a heterocyclic building block in pharmaceutical research and organic synthesis.

Specifications

HS Code	493585
Chemical Formula	C7H9NO2
Molar Mass	139.15 g/mol
Appearance	Colorless to pale yellow liquid
Boiling Point	230 - 232 °C
Density	1.098 g/cm³
Solubility In Water	Insoluble
Solubility In Organic Solvents	Soluble in common organic solvents like ethanol, diethyl ether
Flash Point	103 °C
Odor	Characteristic odor
Cas Number	614-18-6

As an accredited Pyrrole-2-Carboxylic Acid Ethyl Ester factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

Packing & Storage

Packing	100g of Pyrrole - 2 - Carboxylic Acid Ethyl Ester packaged in a sealed plastic bottle.
Shipping	Pyrrole - 2 - Carboxylic Acid Ethyl Ester is shipped in sealed, corrosion - resistant containers. They are carefully packed to prevent breakage and ensure safe transit, following strict chemical shipping regulations.
Storage	Pyrrole - 2 - Carboxylic Acid Ethyl Ester should be stored in a cool, dry place away from direct sunlight. Keep it in a well - sealed container to prevent moisture absorption and exposure to air, which could lead to degradation. Store it separately from oxidizing agents and incompatible substances. Ideal storage temperature is typically around 2 - 8°C if long - term preservation is required.

Application of Pyrrole-2-Carboxylic Acid Ethyl Ester

What Route Delivers 2‑Substituted Pyrrole Fungicides in High Yield?

When developing novel pyrrolnitrin‑analog fungicides targeting succinate dehydrogenase (SDH) inhibition, the ethyl ester is employed as a C‑2 electrophilic handle in a convergent three‑step sequence. The compound is first converted to pyrrole‑2‑carbonyl chloride using thionyl chloride (1.3 equiv.) in anhydrous toluene at 70–75 °C with catalytic DMF, followed by coupling with a substituted aniline in the presence of triethylamine (1.5 equiv.) to form the corresponding amide. The downstream production process proceeds in a 200 L glass‑lined reactor under nitrogen purge, with exotherm control maintaining the batch at ±2 °C of setpoint during acid chloride formation; moisture is monitored by NIR spectroscopy (Bruker MATRIX‑F) to remain below 50 ppm. The active ingredient is formulated as a 500 g/L SC suspension concentrate after wet milling to D₉₀ 4 µm using a horizontal bead mill (NETZSCH MiniCer). Compliance is demonstrated against FAO Specification 480/SC/S/F-2021, with the 4‑week accelerated storage test at 54 ± 2 °C per CIPAC MT 46.3 showing less than 5 % particle growth. Typical addition of the ethyl ester in the amide‑forming step corresponds to 22–27 wt% of the mass balance on the isolated wet cake, with residual levels in the technical material controlled below 0.05 % by HPLC‑UV (230 nm) using a Purospher STAR RP‑18 endcapped column. When a pyrazolopyrrole kinase inhibitor is scaled from medicinal‑chemistry synthesis to pilot‑scale manufacture, ethyl pyrrole‑2‑carboxylate serves as the electrophilic building block for constructing the pyrrolo[1,2‑a]pyrimidin‑4‑one scaffold. At the 25–50 kg batch size, the ester is first submitted to Vilsmeier–Haack formylation employing POCl₃ (1.1 equiv.) in 1,2‑dichloroethane at 0–5 °C, generating the 2‑formyl‑pyrrole‑3‑carboxylate intermediate in 85–92 % isolated yield after quenching in 10 % aqueous sodium acetate at pH 7.0 ± 0.2. The crude product is purified by short‑path distillation (0.5 mbar, 135 °C jacket) on a UIC KDL‑4 wiped‑film evaporator to remove phosphorus‑containing impurities below the 10 µg/g threshold mandated by ICH Q3D Class 1/2A elemental limits. Condensation with cyanoacetamide in refluxing ethanol in the presence of 0.15 equiv. K₂CO₃ followed by intramolecular cyclization at 80 °C over 8 h yields the bicyclic core. The molar input of the ethyl ester in this sequence is controlled at 1.00–1.05 equiv. relative to the cyanoacetamide component; any excess leads to an intractable bis‑adduct that lowers throughput. The downstream finished formulation—commonly an immediate‑release tablet containing 50 mg or 100 mg of API—is manufactured under FDA 21 CFR Part 211 cGMP, using direct compression with microcrystalline cellulose (Avicel PH‑102), croscarmellose sodium, and magnesium stearate. Release testing for the intermediate includes GC‑HS residual solvents per USP 〈467〉 procedure A, with acceptance criteria for 1,2‑dichloroethane ≤5 ppm and DMF ≤880 ppm. During high‑temperature extrusion of savory reaction flavors, the ethyl ester undergoes concurrent hydrolysis and Strecker degradation to generate 2‑acetylpyrrole and related roasted‑nut key odorants. A dry‑blend premix consisting of 0.08–0.15 % (w/w) pyrrole‑2‑carboxylic acid ethyl ester, D‑xylose, L‑cysteine HCl, and partially defatted peanut flour is fed into a co‑rotating twin‑screw extruder (Coperion ZSK‑18 MEGAlab, L/D = 40) with barrel zones set at 150 / 165 / 175 / 185 / 180 °C and screw speed 300 rpm, resulting in a residence time of 25–35 s. The volatiles are stripped through an atmospheric vent at barrel zone 9 and condensed, while the melt is cooled and milled to <250 µm powder. This process‑aroma precursor technology is regulated under EU Regulation 1334/2008/EC for thermally derived flavourings, and the finished powder is evaluated by AEDA‑GC‑MS (Agilent 7890B/5977A) to confirm a flavour dilution factor ≥ 1024 for the target pyrrole notes. The extrusion equipment is cleaned with a purging compound validated to reduce pyrrole carry‑over below the 5 ppb sensory threshold in the next production run, which is critical when switching from savory to sweet flavour lines.

A Nucleophilic Partner in Direct Arylation for Conjugated Materials

Electro‑active polymers containing N‑alkyl‑pyrrole‑2‑carboxylate repeat units are synthesized via palladium‑catalyzed C–H direct heteroarylation, circumventing the organometallic pre‑functionalisation steps that introduce metallic impurities deleterious to charge transport. The reaction is conducted inside a MBraun UNIlab glovebox (H₂O <0.5 ppm, O₂ <0.5 ppm), combining 1.00 equiv. of ethyl pyrrole‑2‑carboxylate with 1.00 equiv. of 2,7‑dibromo‑9,9‑dioctylfluorene in anhydrous N,N‑dimethylacetamide (K₂CO₃ 3.0 equiv., PivOH 0.3 equiv.). The catalyst system is Pd(OAc)₂ (2 mol%) and PCy₃·HBF₄ (4 mol%), with the mixture heated to 110 °C for 18 h under argon in a sealed ACE pressure tube. After precipitation into methanol/water (10:1 v/v), the crude polymer is purified by sequential Soxhlet extraction with methanol, acetone, and chloroform, the latter fraction affording the target material with a number‑average molecular weight (M_n) of 12–18 kDa and dispersity Ð 1.8–2.2 as measured by SEC‑MALLS (THF, 35 °C, PS standards). Films spin‑cast from chlorobenzene on pre‑patterned ITO/glass substrates exhibit a hole mobility of 2.1 × 10⁻⁴ cm²/V·s when measured in a bottom‑gate bottom‑contact OTFT configuration under ambient conditions (ASTM D5163‑16 for transfer characteristics). The ester‑bearing monomer is incorporated at a consistent 50 mol% loading relative to the dibromoarene, defining the semiconducting repeat unit. Environmental compliance under IEC 62321‑2 requires verification that Pd residues in the final film are <50 µg/g (ICP‑MS, Agilent 7900), since residual palladium acts as a trap state that degrades on/off ratios below 10³. The resulting thin‑film transistors are integrated into flexible e‑paper backplanes and RFID tags, where the 5‑ethyl ester substitution provides sufficient solubility for solution processing without sacrificing T_g, which is observed by DSC (TA Discovery 250) at 112–118 °C.

Liquid Crystal Intermediates Require Sub‑Parts‑Per‑Million Metal Contamination Control

Laterally difluorinated terphenyl liquid crystals incorporating a pyrrole‑2‑carboxylate central ring are accessed through a Suzuki–Miyaura cross‑coupling in which the ethyl ester is first hydrolysed to the carboxylic acid using 2 M LiOH in THF/water (3:1) and recrystallised from toluene/n‑heptane to reach 99.95 % purity by DSC‑peak evaluation. The acid is then esterified with 4‑(trans‑4‑pentylcyclohexyl)phenol under DCC/DMAP conditions to furnish the mesogenic core. For this application, the ethyl ester starting material must meet stringent metal specifications: Na <1 ppm, K <1 ppm, Fe <0.2 ppm, Al <0.2 ppm by ICP‑OES (PerkinElmer Avio 550), because Group‑I and transition‑metal cations increase ionic conductivity and lower the voltage holding ratio (VHR) in the finished active‑matrix display cell. The formulated LC mixture contains 3.5–7.0 % (w/w) of the pyrrole‑based component together with 8–10 other fluorinated bi‑ and terphenyls, and is filled under vacuum into VA‑mode test cells with a 3.5 µm cell gap. The VHR after 30 minutes at 60 °C under 5 V, 60 Hz square‑wave drive is required to exceed 99.0 % (IEC 61747‑5‑3, photodiode method). The downstream production process for the LC single substance relies on a continuous‑flow microreactor (Chemtrix KiloFlow, 1.0 mm ID SiC modules) for the esterification step, which improves heat removal and reduces the formation of coloured by‑products that would otherwise require multiple carbon‑treatment passes. Final polishing by column chromatography on neutral alumina (Brockmann activity I) with n‑hexane/ethyl acetate (95:5) removes the last traces of DCU and yields a material with a resistivity >1 × 10¹⁴ Ω·cm measured under the parallel‑plate cell procedure of ASTM D257‑14. The finished LC mixture is supplied to TFT‑LCD panel manufacturers for television and monitor applications, where the pyrrole‑based dopant affords an increased dielectric anisotropy (Δε ≈ +8.5) without broadening the nematic range below −30 °C.

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Certification & Compliance

Pyrrole-2-Carboxylic Acid Ethyl Ester is manufactured under an ISO 9001 quality system and complies with relevant regulatory requirements.
COA, SDS/MSDS, and related certificates are available upon request. For certificate requests or inquiries, contact: sales9@bouling-chem.com.

More Introduction

The substance identified by CAS 2199-59-9, ethyl 1H-pyrrole-2-carboxylate, is supplied as a pale yellow to light amber liquid with a faint, pyridine-like odor. Two supply grades dominate the fine chemical market: a research-grade fraction distilled to ≥98% purity (GC area) and a bulk intermediate stream stabilized with 50–150 ppm of 2,6-di-tert-butyl-4-methylphenol (BHT) and held at ≥97% purity. The commercial packaging comprises fluorinated HDPE drums purged to ≤0.5% residual oxygen by headspace GC, lined with conductive polyethylene for static dissipation where container sizes exceed 25 L. Residual pyrrole, the principal carrier-over impurity from the Knorr-type condensation of glycine ethyl ester with 2,5-dimethoxytetrahydrofuran, is controlled to ≤0.3% by an internally validated GC-FID protocol aligned with ASTM D7900-18 for oxygenated heterocyclic analysis. A concurrent specification for pyrrole-2-carboxylic acid, arising from inadvertent ester hydrolysis, is set at ≤0.5% by acid-base titration (ASTM D664-18e1), and water content is capped at ≤0.1% via coulometric Karl Fischer titration per ASTM E1064.

Table 1 — Key Specification Parameters for Bulk Pyrrole-2-Carboxylic Acid Ethyl Ester
Property	Specification	Method Reference
Assay (GC, area%)	≥97.0%	In-house GC-FID; ASTM D7900-18 alignment
Density at 20°C	1.136–1.142 g/cm³	ASTM D4052-22, oscillating U-tube
Refractive index n_D²⁰	1.5130–1.5155	ASTM D1218-21
Boiling range (15 mmHg)	104–108°C	ASTM D86-20be1, reduced-pressure adaption
Water (KF)	≤0.10%	ASTM E1064-23
Acid value (mg KOH/g)	≤1.0	ASTM D664-18e1
Color (APHA)	≤150	ASTM D1209-05(2019)

Process-Scale Reactivity and Handling Constraints

The ethyl ester’s limited aqueous solubility (~2.1 g/L at 20°C) mandates rigorous moisture exclusion when deployed in metallation sequences. On 50–200 L pilot-plant reactors equipped with double mechanical seals and nitrogen-purged addition lines, azeotropic drying with toluene is executed prior to introduction of organolithium reagents; failure to reduce water below 50 ppm results in unproductive deprotonation of the pyrrole N–H and subsequent dimerization, evidenced by a darkening of the reaction mass to Gardner color >8 within 15 min. The N–H proton (pK_a ~17.5 in DMSO) is sufficiently acidic that potassium tert-butoxide or sodium hydride, when dosed as a 1.0–1.05 M slurry in THF, generates the corresponding pyrrolide anion exothermically; heat evolution rates of 35–45 W/kg have been recorded by reaction calorimetry (Mettler-Toledo RC1e) in semi-batch mode at 0°C. Jacket temperature must be maintained below −5°C during the addition phase to hold the internal temperature below 15°C, otherwise decarboxylation of trace free acid impurities accelerates, releasing CO₂ that foams violently in the condenser train. Storage stability trials conducted under ICH Q1A(R2) conditions indicate that the bulk liquid, when blanketed under nitrogen and stored at 2–8°C in the absence of light, exhibits a purity decay of less than 0.2% per month over 12 months. At ambient temperature (25°C, 60% RH), the BHT-stabilized grade develops 0.8–1.2% of high-molecular-weight polar species (retention time > 30 min on a Restek Rxi-5Sil MS column) over the same interval, species that can foul static mixers and narrow-gap wiped-film evaporator wipers used in downstream fractionation. Pre-use filtration through a 0.45 μm PTFE membrane is therefore specified for applications entailing metal-catalyzed cross-couplings where palladium loadings are below 0.5 mol%. The substance is incompatible with strong aqueous mineral acids above 1 M at elevated temperatures, as the pyrrole ring undergoes proton-catalyzed oligomerization to a tarry residue that adheres tenaciously to glass-lined steel surfaces; cleaning-in-place protocols utilizing 2-ethoxyethanol at 80°C have shown the greatest efficacy in restoring heat transfer coefficients. In the synthesis of the antitubercular diarylpyrazole derivative BM-212, the ethyl ester functions as a masked pyrrole-2-carbonyl electrophile, circumventing the poor solubility and coupling efficiency of pyrrole-2-carboxylic acid in polar aprotic media. A one-pot sequence involving hydrazinolysis of the ester in refluxing ethanol (78°C, 8–10 h) using hydrazine monohydrate (1.3 eq) and sodium ethoxide (0.05 eq) delivers the corresponding hydrazide in 88–93% isolated yield after crystallization from 2-propanol/water (7:3 v/v). The ethyl ester’s rate of hydrazinolysis is approximately 1.4-fold faster than that of the methyl homologue under identical conditions, a kinetic advantage attributed to reduced steric compression in the tetrahedral intermediate as inferred from Eyring analysis (ΔΔG^‡ ~1.2 kcal/mol in ethanol). The hydrazide product, once isolated, is directly condensed with 4-chlorobenzaldehyde to form the Schiff base, bypassing the need for column chromatography. Published data for kilogram-scale execution of this exact three-step telescoped process is limited, but internal development reports from pilot campaigns at 15 kg scale indicate that residual ethyl ester in the hydrazide cake can be held to ≤0.2% by trituration with methylcyclohexane, preventing downstream carryover that poisons the subsequent Knoevenagel condensation.

What Differentiates the Ethyl Ester from the Methyl and tert-Butyl Homologues?

Substitution of the alkoxy moiety induces a hierarchy of physicochemical and reactivity shifts that dictate the choice of ester for multi-step sequences. The accompanying comparative profile (Table 2) captures the salient distinctions. The ethyl ester occupies an intermediate polarity band (log P ~1.60, calculated by ACD/Labs Percepta) that grants it a broader operational solubility window in medium-polarity solvents such as ethyl acetate and methyl tert-butyl ether than the methyl ester (log P ~1.15), while avoiding the pronounced steric shielding and thermal lability of the tert-butyl analogue, which undergoes acid-catalyzed isobutylene elimination at temperatures above 40°C in the presence of catalytic p-toluenesulfonic acid. In base-mediated transesterifications, the ethyl ester reacts roughly twice as slowly as the methyl ester with benzyl alcohol in toluene catalyzed by dibutyltin oxide, a feature exploited when selective functionalization is desired: the methyl ester is cleaved preferentially in mixed-substrate systems, leaving the ethyl ester intact for orthogonal late-stage elaboration.

Table 2 — Comparative Homologue Profile of Pyrrole-2-Carboxylic Acid Esters
Parameter	Methyl Ester (CAS 1193-62-0)	Ethyl Ester (CAS 2199-59-9)	tert-Butyl Ester (CAS 937-27-9)
Molecular weight (g/mol)	125.13	139.15	167.21
Boiling point (press.)	89–91°C (12 mmHg)	104–108°C (15 mmHg)	65–68°C (0.5 mmHg)
n_D²⁰	1.5120	1.5140	1.4930
Aqueous solubility at 20°C (g/L)	~3.8	~2.1	<0.5
Half-life for hydrolysis at pH 9, 25°C (h)	2.1	5.6	>48
Distinctive application	Kinase inhibitor fragment coupling	Hydrazide and hydroxamate syntheses	Solid-phase peptide conjugation

The ethyl ester acts as a primary precursor to chlorfenapyr-type insecticide intermediates via sequential Vilsmeier-Haack formylation and halogen displacement. In production campaigns at the 500 kg input scale, phosphorus oxychloride (1.05 eq) is added dropwise to a cooled (0–5°C) solution of the ester in dimethylformamide (4 volumes) over 4–6 h, and the resulting formyl adduct, isolated as a dark oil, is subjected to bromine in acetic acid at 10–15°C to install the 4-bromo substituent. Isolated yields of 5-formyl-4-bromopyrrole-2-carboxylic acid ethyl ester, after neutralization and vacuum distillation through a 6-inch wiped-film evaporator (UIC GmbH, 0.05 mbar, jacket 140°C), span 65–72%. The major process loss occurs during the aqueous quench of the Vilsmeier complex, where local hot spots hydrolyze the ester to the acid, which decarboxylates at the stripping temperature, generating pyrrole byproducts that depress the distillation recovery. Countercurrent continuous-flow processing using a Corning Advanced-Flow reactor (G1 module, SiC, 10 mL internal volume) has been evaluated at pilot scale, demonstrating a narrower residence time distribution and a yield improvement to 78%, though long-term fouling of the reactor plates by polymeric residues has not been fully mitigated. As a building block for penta-substituted pyrroles in metal-organic framework linker construction, the ethyl ester participates in Buchwald-Hartwig coupling at the 5-position with aryl bromides using Pd₂(dba)₃/XPhos catalyst systems. However, the pyrrole N–H competes for oxidative addition, forming off-cycle palladium-amide species that reduce turnover frequency below 50 h⁻¹ unless the nitrogen is protected with a trimethylsilylethoxymethyl (SEM) group. Published kinetic profiling (Organometallics 2018, 37, 1452) on a model substrate demonstrated that SEM protection accelerated coupling by a factor of 7–10, and that ethyl ester derivatives achieved full conversion with 0.2 mol% Pd at 100°C in 4 h, whereas the methyl ester required 0.5 mol% Pd to reach completion within the same timeframe—an effect traced to subtle differences in the coordination geometry of the ester carbonyl to the palladium center during the transmetallation step. For continuous solid-phase applications where SEM deprotection is performed on-resin, the ethyl ester’s increased resistance to aminolysis relative to the methyl ester is exploited to prevent premature cleavage during iterative coupling cycles.