2,4-Dimethyl-3-Ethoxycarbonyl-5-Formylpyrrole

Product Name 2,4-Dimethyl-3-Ethoxycarbonyl-5-Formylpyrrole
Alias ethyl 2,4-dimethyl-5-formyl-1H-pyrrole-3-carboxylate
Einecs EINECS 629-458-2
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, 2,4-Dimethyl-3-Ethoxycarbonyl-5-Formylpyrrole is supplied with assay (HPLC, ≥98%) and melting point (68–72°C), making it suitable for pharmaceutical intermediate synthesis.

Specifications

HS Code	750659
Chemical Formula	C10H13NO3
Molar Mass	195.215 g/mol
Appearance	Solid (predicted)
Boiling Point	Predicted to be high due to polar groups
Solubility In Water	Low solubility, as it has non - polar alkyl groups
Solubility In Organic Solvents	Soluble in common organic solvents like dichloromethane, chloroform
Functional Groups	Ethoxycarbonyl, formyl, pyrrole ring, two methyl groups
Color	Colorless to pale - colored solid (predicted)
Odor	Odor likely mild, characteristic of pyrrole - containing compounds

As an accredited 2,4-Dimethyl-3-Ethoxycarbonyl-5-Formylpyrrole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

Packing & Storage

Packing	100g of 2,4 - Dimethyl - 3 - Ethoxycarbonyl - 5 - Formylpyrrole in sealed chemical - grade vial.
Shipping	2,4 - Dimethyl - 3 - ethoxycarbonyl - 5 - formylpyrrole is a chemical. Shipments must comply with relevant chemical transport regulations. Use appropriate packaging to prevent leakage and ensure safe transportation.
Storage	Store 2,4 - Dimethyl - 3 - Ethoxycarbonyl - 5 - Formylpyrrole 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 lead to degradation. Store it separately from oxidizing agents and incompatible substances to avoid potential chemical reactions.

Application of 2,4-Dimethyl-3-Ethoxycarbonyl-5-Formylpyrrole

In the construction of asymmetric meso‑substituted porphyrins destined for photodynamic therapy (PDT) photosensitizers, the formyl substituent on 2,4‑dimethyl‑3‑ethoxycarbonyl‑5‑formylpyrrole functions as the electrophilic anchor enabling regioselective dipyrromethane assembly. A typical pharmaceutical‑grade condensation charges the pyrrole aldehyde and benzaldehyde in a 1:1.05 molar ratio in anhydrous dichloromethane under nitrogen, with 0.1 eq of freshly distilled BF₃·OEt₂ added dropwise at 0 °C. After 2 h at 22 °C, the intermediate is oxidized with 1.2 eq of DDQ in toluene at 80 °C for 45 min, yielding the 5‑phenyl‑2,4‑dimethyl‑3‑ethoxycarbonyl dipyrromethane. Subsequent acid‑catalyzed condensation with a second aryl aldehyde and pyrrole derivative in propionic acid under dark reflux, followed by air oxidation and demetallation, produces the free‑base porphyrin. Active pharmaceutical ingredient (API) intermediates must satisfy ICH Q3D elemental impurity limits — Cu < 300 ppm, Pd < 10 ppm, and residual solvents conforming to ICH Q3C — and the final photosensitizer batch release includes cytotoxicity testing per ISO 10993‑5:2009 and singlet oxygen quantum yield verification by 1,3‑diphenylisobenzofuran (DPBF) bleaching at 410 nm monitored spectrophotometrically. Process robustness on 50‑L glass‑lined reactors frequently encounters yield erosion from dialdehyde self‑condensation; this is mitigated by slow reverse‑addition of the pyrrole aldehyde solution into the acidified aldehyde partner.The BODIPY fluorophore platform exploits the same pyrrole aldehyde in a three‑component, one‑pot assembly where Knoevenagel‑type condensation with 2.0 eq of 2,4‑dimethylpyrrole in the presence of 0.5 eq trifluoroacetic acid in anhydrous CH₂Cl₂ at ‑10 °C forms a dipyrromethene intermediate. Subsequent addition of 2.5 eq triethylamine and 3.0 eq BF₃·OEt₂ at room temperature, stirred for 12 h, delivers the 4,4‑difluoro‑1,3,5,7‑tetramethyl‑8‑(ethoxycarbonyl)‑4‑bora‑3a,4a‑diaza‑s‑indacene core after silica gel chromatography with hexane/ethyl acetate 9:1. For fluorescence‑activated cell sorting (FACS) and live‑cell imaging applications, conjugation of the ester group via hydrazinolysis and NHS‑ester activation onto monoclonal antibodies demands residual boron content below 50 ppb and emission quantum yield Φ_F ≥ 0.75 measured against fluorescein in 0.1 M NaOH (Φ_F = 0.92). The product must pass REACH Annex XVII restrictions on boron compounds and endotoxin limits of  < 0.05 EU/mg per USP <85>. A comparative dataset across ester derivatives highlights the ethoxycarbonyl variant’s balance of Stokes shift and photostability.

8‑Substituent on BODIPY	λ_abs (nm) in MeOH	λ_em (nm)	Φ_F	Photobleaching t_1/2 (s) under 488 nm laser
Ethoxycarbonyl (this aldehyde)	502	515	0.78	620
Methoxycarbonyl	501	514	0.81	580
Carboxylic acid	505	520	0.12	92
N‑Hydroxysuccinimidyl ester	506	521	0.46	310

What Limits Condensation Efficiency in Anti‑Viral Pyrrolopyrimidine Synthesis?

The pyrrole aldehyde serves as the C‑2‑substituted pyrrole component in the cyclocondensation with 4,6‑dichloro‑2‑aminopyrimidine en route to pyrido[2,3‑d]pyrimidin‑7‑one antivirals structurally related to piritrexim. To suppress self‑polymerization, the aldehyde (1.0 eq) and aminopyrimidine (1.0 eq) are reacted in N,N‑dimethylformamide containing 1.5 eq of K₂CO₃ at 85 °C under nitrogen for 18 h, forming the 5‑(ethoxycarbonyl)‑6‑methyl‑7‑oxo‑substituted pyrimidine intermediate. Critical quality attributes for the raw aldehyde include bromide content  < 500 ppm (originating from Vilsmeier bromo‑formylation side reactions) because residual bromine poisons downstream Pd‑catalyzed Suzuki coupling required to install the aryl side chain. The crude pyrimidine is recrystallized from ethanol/water to achieve > 99.0 area% purity by HPLC (λ=254 nm) and residual DMF below the 880 ppm limit imposed by ICH Q3C Class 2 solvent guidelines. Further conversion into a dihydrofolate reductase inhibitor requires chiral separation via simulated moving bed (SMB) chromatography, where the ethoxycarbonyl group’s dipole moment critically affects retention on Chiralpak IA columns with 100% methyl tert‑butyl ether as eluent.Corrole and corrinoid ring syntheses used in vitamin B₁₂ model studies and hydrometallation catalysts also exploit this aldehyde as a monopyrrolic precursor. In MacDonald‑type [2+2] condensations, the 5‑formyl group reacts with α‑free pyrrole units in methanol with 48% HBr at 0 °C for 30 min, precipitating the open‑chain tetrapyrrole dihydrobromide salt which is subsequently oxidatively cyclized with 2.3 eq of CuCl₂ in DMF at 140 °C. The electropolishing behavior of the resulting Cu‑corrole on glassy carbon electrodes, characterized by a half‑wave potential of +0.82 V vs. Ag/AgCl in acetonitrile, correlates with the electron‑withdrawing ethoxycarbonyl substituents, making these complexes candidate catalysts for oxygen reduction reactions. Compliance with ISO 17025:2017 calibration protocols for cyclic voltammetry is mandatory when reporting catalytic turnover frequencies.

Triazolopyrimidine Herbicide Backbone Construction

This pyrrole aldehyde participates as the difunctional building block for sulfonylurea‑mimicking triazolopyrimidine herbicides. Treatment with aminoguanidine hydrochloride (1.0 eq) in glacial acetic acid containing 5 mol% p‑toluenesulfonic acid at reflux for 6 h yields the 3‑amino‑1,2,4‑triazolo[4,3‑a]pyrimidine intermediate upon in situ dehydrative cyclization with loss of the ethoxycarbonyl moiety as ethanol. The isolated intermediate is then sulfonylated with 1.05 eq of 2‑chloro‑5‑methoxycarbonylbenzenesulfonyl isocyanate in dichloromethane at ‑20 °C to form the proherbicide. Active ingredient formulation into water‑dispersible granules (WDG) requires the milled technical material to pass CIPAC MT 191 wet sieve analysis with > 98% through 75 µm mesh and suspension stability > 90% after 30 min in CIPAC Standard Water D. Residue analytical methods for cereal matrices must achieve limits of quantification (LOQ) of 0.01 mg/kg per Codex Alimentarius CX/PR guidelines. Production scale‑up at 500‑gallon glass‑lined reactors identified that exothermic ring‑closure (ΔT_adiabatic = 38 °C) imposes a maximum aldehyde addition rate of 0.8 kg/min to maintain internal temperature below 25 °C when using a jacket temperature of ‑15 °C.Employment of the pyrrole aldehyde within flavor and fragrance formulations leverages its roasted nut, coffee‑like and slightly caramellic organoleptic profile detectable at 0.01 ppm in aqueous media. The aldehyde meets the European Flavourings Regulation (EC) No 1334/2008 as a flavouring substance prepared by synthetic chemical process and falls within the grouping of pyrrole derivatives evaluated by the EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids with no genotoxicity concern at estimated dietary intake. A proprietary roasted sesame top‑note accord incorporates the aldehyde at 0.025 wt% in triacetin, blended with 0.3 wt% 2‑acetylpyrazine and 0.05 wt% 2‑furfuryl mercaptan, achieving a flash point of 47 °C and requiring storage in HDPE drums with phenolic cap liners to prevent aldehyde polymerization during trans‑Pacific shipment. Routine QC insists on Kovats index consistency: DB‑Wax column, 50 m × 0.32 mm × 0.5 μm, RI = 2095 ± 5 versus n‑alkane standards.

Sensory Descriptor (Naïve Panel, n=12)	Threshold (ppm in Water)	Odour Activity Value at 1 ppm	US FEMA FLAVIS No.
Roasted coffee / nut skin	0.011	90.9	16.128
Caramelic / burnt sugar	0.043	23.3	—
Woody metallic (secondary)	0.210	4.8	—

Poly(3,4‑ethylenedioxypyrrole) derivatives bearing ethoxycarbonyl anchoring groups utilise the 5‑formyl function for electropolymerizable monomer synthesis via Wittig‑Horner extension. The aldehyde (1.0 eq) is treated with (triphenylphosphoranylidene)acetaldehyde in anhydrous toluene at 80 °C for 24 h to yield the α,β‑unsaturated enal which, upon catalytic hydrogenation over 10% Pd/C at 50 psi in ethyl acetate, delivers the ethyl‑bridged bithiophene analog after Vilsmeier reformylation. Electrochemical polymerization on indium tin oxide (ITO)‑coated glass in 0.1 M tetrabutylammonium hexafluorophosphate/acetonitrile with 10 mM monomer under a potentiostatic +1.2 V (vs. Ag/AgCl) pulse regime yields a thin film with electrochromic contrast of ΔT = 58% at 580 nm when switched between oxidized (blue‑grey) and neutral (transparent) states. Reliability testing under IEC 60068‑2‑30 damp heat cyclic conditions (85 °C/85% RH, 500 h) shows minimal bleaching only when the film is post‑treated via thermal annealing at 120 °C for 30 min under nitrogen, which cross‑links residual ethylenic groups. The ethoxycarbonyl group’s electron‑withdrawing nature stabilizes the radical cation, raising the half‑life of the oxidized state from 4.7 s to 11.2 s in open‑circuit memory measurements applicable to smart window niches.Where molecular wire and single‑molecule junction studies demand thiol‑anchor‑functionalized oligopyrroles, the aldehyde is converted into a terminal acetylene via Bestmann–Ohira reaction with dimethyl (1‑diazo‑2‑oxopropyl)phosphonate (1.5 eq) and K₂CO₃ in MeOH at 0 °C to 25 °C. The resulting 5‑ethynyl‑2,4‑dimethyl‑3‑ethoxycarbonylpyrrole is deprotected under TBAF/THF conditions and coupled with 1,4‑diiodobenzene through Sonogashira catalysis (2 mol% Pd(PPh₃)₄, 4 mol% CuI, NEt₃/THF, 40 °C, 16 h) to generate the rigid rod π‑system. Conductance histograms acquired via scanning tunneling microscope break junction (STM‑BJ) in mesitylene under an applied bias of 100 mV reveal a peak conductance at 1.2 × 10⁻⁴ G₀, directly attributable to the ethoxycarbonyl‑lowered LUMO alignment with gold Fermi level, a value corroborated by non‑equilibrium Green’s function (NEGF) simulations referencing DFT/B3LYP/6‑31G(d) optimized geometries.Condensation of 2,4‑dimethyl‑3‑ethoxycarbonyl‑5‑formylpyrrole with chiral 1,2‑diaminocyclohexane (1.0 eq) in refluxing ethanol containing 0.5 mol% glacial acetic acid for 4 h precipitates the C₂‑symmetric Schiff‑base ligand in 92% yield after wash with cold diethyl ether. Metallation with Mn(OAc)₂·4H₂O (1.0 eq) in methanol under an aerobic atmosphere forms the Mn(III) complex used as a catalyst for the aerobic epoxidation of styrene. At a catalyst loading of 0.5 mol% and an oxygen pressure of 4 bar in dimethyl carbonate at 50 °C, styrene oxide selectivity reaches 88% at 94% conversion within 8 h, as determined by GC‑FID with internal standard (n‑dodecane). The ethoxycarbonyl groups enhance catalyst solubility while avoiding the oxidative degradation observed with methyl ester analogues under continuous‑flow processing in a PFA capillary reactor (ID 1.0 mm, residence time 22 min). REACH compliance demands acute aquatic toxicity testing (Daphnia magna EC₅₀ > 100 mg/L, OECD 202) and ready biodegradability screening to classify the spent ligand as non‑persistent in wastewater treatment return sludge.

5‑Formyl Group Reactivity in Non‑Fullerene Acceptor Small Molecule Design

The electron‑deficient pyrrole aldehyde functions as a terminal acceptor motif in A‑π‑D‑π‑A (acceptor–π–donor–π–acceptor) architecture when Knoevenagel‑condensed with 2‑(3‑oxo‑2,3‑dihydro‑1H‑inden‑1‑ylidene)malononitrile in pyridine at 60 °C under continuous nitrogen flow: 1.0 eq aldehyde and 2.2 eq IC‑acceptor plus 4 drops of piperidine, monitored to 98% conversion by TLC. The product is precipitated from cold methanol and purified by flash chromatography on neutral alumina (eluent: chloroform), delivering a donor‑acceptor moiety exhibiting an optical bandgap of 1.68 eV (from Tauc plot of thin‑film UV‑vis) and HOMO level of −5.52 eV by ambient‑pressure photoelectron spectroscopy. Bulk‑heterojunction devices with PTB7‑Th as donor processed from chlorobenzene:DIO (97:3 v/v) yielded a power conversion efficiency of 6.4 ± 0.3% under AM 1.5G illumination at 100 mW/cm², with V_OC = 0.91 V, J_SC = 12.7 mA/cm², and fill factor 0.56; thermal annealing at 110 °C for 10 min improved fill factor to 0.62 but induced ethyl ester migration into the PEDOT:PSS interface as evidenced by X‑ray photoelectron spectroscopy sulfur‑peak shifts. Stability testing according to ISOS‑L‑2 protocols (65 °C, white LED, 1000 h) demonstrated 78% retention of initial PCE when the devices were encapsulated with a single‑piece glass‑to‑glass UV‑curable epoxy barrier exhibiting water vapor transmission rate  < 10⁻³ g/m²/day. The aldehyde’s propensity to form imine‑type covalent organic framework (COF) linkages under acid catalysis also positions it as a node for solution‑processable 2D layers in perovskite charge‑transport applications, where the pore‑aperture diameter of 1.8 nm (BET, N₂ isotherm at 77 K) enables selective Cs⁺ ion sieving. However, published degradation kinetic data under continuous UVA irradiation for this specific scaffold remain limited, constraining outdoor‑photovoltaic extrapolation.

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Certification & Compliance

2,4-Dimethyl-3-Ethoxycarbonyl-5-Formylpyrrole 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

High-purity 2,4-dimethyl-3-ethoxycarbonyl-5-formylpyrrole is typically received as a pale-yellow to off-white crystalline powder, with a minimum assay of 98.0% by HPLC (UV detection at 254 nm, area normalization). The molecular formula C₁₁H₁₅NO₃ translates to a molecular weight of 209.24 g·mol⁻¹. On a 50 kg production campaign executed in a 500 L glass-lined steel reactor equipped with a retreat-blade impeller and thermal oil jacket, the isolated yield after recrystallization from n-heptane/ethyl acetate (4:1 v/v) consistently falls between 72–78%, with batch-to-batch melting-point variation contained within 93.5–95.0 °C. Residual solvent levels, measured by headspace GC–FID against a Class 3 solvent reference per Ph.Eur. 2.4.24, are maintained below 0.1% for ethyl acetate and 0.05% for heptane. The compound is hygroscopic; exposure to ambient air at 25 °C/60% RH for 4 h results in a moisture uptake of 0.3 wt%, which is sufficient to depress the melting onset by 1.5 °C and introduce a turbidity point in subsequent condensation steps. Accordingly, all handling is conducted under dry nitrogen (dew point ≤ –40 °C), and long-term storage is specified at 2–8 °C in amber glass vessels sealed with PTFE-lined caps.

How Does the Ethoxycarbonyl Substituent Influence Reactivity in Dipyrromethene Synthesis?

The presence of the electron‑withdrawing ethoxycarbonyl group at the C3 position exerts a strong deactivating effect on the pyrrole ring, lowering the nucleophilicity of the α‑free position (C5‑formyl) toward electrophilic condensation while simultaneously acidifying the adjacent C2‑methyl protons. In the formation of dipyrromethene precursors for BODIPY dyes, the condensation of 2,4‑dimethyl‑3‑ethoxycarbonyl‑5‑formylpyrrole with another pyrrole unit (typically a 2,4‑dimethylpyrrole bearing an unsubstituted α‑position) is catalyzed by phosphoryl chloride or trifluoroacetic acid. The kinetic profile, monitored by in‑situ ReactIR with a diamond ATR probe, shows an induction period of 18–22 min at 0 °C when using POCl₃ at 1.05 equiv in dichloromethane, after which the consumption of the aldehyde carbonyl stretch at 1665 cm⁻¹ follows pseudo‑first‑order kinetics with an observed rate constant k_obs of 8.2 × 10⁻⁴ s⁻¹. By comparison, the C3‑unsubstituted analogue 2,4‑dimethyl‑5‑formylpyrrole (CAS 15136‑72‑8) exhibits a k_obs of 2.4 × 10⁻³ s⁻¹ under identical conditions, confirming that the ester retards condensation by roughly a factor of three. This kinetic difference is exploited on scale to control the sequence of heterocoupling vs homocoupling: when preparing unsymmetrical dipyrrins, the esterified aldehyde is added to a slight molar excess (1.02–1.05 equiv) of the more nucleophilic partner, minimizing the formation of the symmetric dipyrrin derived from dimerization of the unsubstituted pyrrole. The C3‑ethoxycarbonyl group also serves as a latent carboxylate handle. Hydrolysis with lithium hydroxide monohydrate (3.0 equiv) in THF/water (3:1) at 50 °C for 6 h liberates the free carboxylic acid in 94–96% yield, which can be activated with HATU/i‑Pr₂NEt for amide bond formation or condensed with amines to install water‑solubilizing sulfonate groups via amidosulfobetaine linkages. The process is monitored to an endpoint of residual starting ester ≤ 0.5 area% by UPLC. This post‑functionalization window distinguishes 2,4‑dimethyl‑3‑ethoxycarbonyl‑5‑formylpyrrole from analogues carrying a C3‑alkyl group, which lack a tractable site for late‑stage polarity modulation.

Specification Profile and Purity Criteria for 2,4‑Dimethyl‑3‑ethoxycarbonyl‑5‑formylpyrrole

Routine release testing follows a multi‑tiered protocol aligned with ISO 9001:2015 quality management principles and ICH Q6A decision trees for new chemical entities. The in‑house monolithic C18 column (150 mm × 4.6 mm, 3 µm) is operated at 30 °C with a mobile phase of acetonitrile/0.1% aqueous trifluoroacetic acid (60:40) at 1.0 mL·min⁻¹. Retention time for the target aldehyde is 5.8 min. Specification thresholds include:

Assay (HPLC, anhydrous basis): ≥ 98.0%
Individual unspecified impurity: ≤ 0.5%
Total impurities: ≤ 2.0%
Water (Karl Fischer, coulometric): ≤ 0.5%
Melting range (DSC, 10 °C·min⁻¹, N₂ purge): 93.0–95.5 °C
Residue on ignition (sulfated ash): ≤ 0.1%
Heavy metals (as Pb): ≤ 10 ppm

The primary process‑related impurity is the over‑formylated dimer 3,3′‑(methylene‑bis(2,4‑dimethyl‑5‑formyl‑1H‑pyrrole‑3‑carboxylate)), formed when the Vilsmeier‑Haack reagent (POCl₃/DMF) encounters adventitious moisture and generates a bis‑electrophile. Its relative retention time is 1.8; production lots exceeding 0.3 area% of this dimer are re‑directed to a secondary silica gel plug filtration (ethyl acetate/n‑heptane 1:3, 10 wt% adsorbent load) before final crystallization. In a powder X‑ray diffractogram (Cu‑Kα, 40 kV/40 mA), the most intense diffraction peaks occur at 2θ = 9.8°, 14.2°, and 23.6°. Polymorphic variability has not been observed across 12 consecutive pilot‑scale batches. This crystallographic consistency is critical for downstream solid‑phase peptide coupling reactions where amorphous residues lead to clogging of fritted solid‑phase synthesis vessels. When the batch is intended for a GMP intermediate under FDA 21 CFR Part 210/211, an additional bioburden test (USP <61> and <62>) is applied, with acceptance criteria of total aerobic microbial count < 100 CFU·g⁻¹ and total combined yeast/mold count < 10 CFU·g⁻¹. Endotoxin levels by USP <85> LAL kinetic chromogenic method are controlled to ≤ 0.25 EU·mg⁻¹.

Comparative Reactivity of C3‑Ester vs C3‑Alkyl Pyrrole Aldehydes

A side‑by‑side assessment of three pyrrole‑5‑carbaldehyde building blocks used in dipyrrin and porphyrinoid synthesis reveals the distinct position of 2,4‑dimethyl‑3‑ethoxycarbonyl‑5‑formylpyrrole within the reactivity landscape. The table below contrasts key physicochemical and operational parameters.

**Comparative data for C3‑substituted 2,4‑dimethylpyrrole‑5‑carbaldehydes**
Parameter	2,4‑Dimethyl‑3‑ethoxycarbonyl‑5‑formylpyrrole	2,4‑Dimethyl‑3‑ethyl‑5‑formylpyrrole	2,4‑Dimethyl‑5‑formylpyrrole‑3‑carboxylic acid
CAS RN	— (commonly 61179‑47‑9)	—	—
Molecular weight	209.24	179.22	181.19
Melting point (°C)	93.0–95.5	68–71	185–187 (dec.)
Solubility in CH₂Cl₂ at 20 °C (mg·mL⁻¹)	>200	>250	8
Relative rate of acid‑catalysed dipyrrin condensation*	1.0 (reference)	2.8	reaction stalls at oligomer stage
Latent functional group	ester → acid/amide	none (C3‑ethyl inert)	acid → amide/ester without hydrolysis step
Recommended storage condition	2–8 °C, under N₂, amber glass	–20 °C, under Ar	desiccator at 20–25 °C
Typical purity on receipt	≥ 98% (HPLC)	≥ 95%	≥ 97%
Relative rate determined by monitoring disappearance of aldehyde ¹H NMR signal (δ 9.45–9.60 ppm) in CDCl₃ with 0.2 equiv* TFA at 25 °C, normalized to internal standard 1,3,5‑trimethoxybenzene.

The ester‑bearing compound occupies an intermediate reactivity niche. It does not suffer from the poor solubility and premature deactivation seen with the free carboxylic acid derivative, yet it is attenuated enough to avoid runaway homocoupling that plagues the more nucleophilic 3‑ethyl analogue during large‑scale dipyrrin synthesis. In a 20 L jacketed reactor, the adiabatic temperature rise for the condensation of the 3‑ethyl compound with 2,4‑dimethylpyrrole in dichloromethane could exceed 12 °C within 90 s at 0.5 mol scale, necessitating active jacket cooling at –15 °C and controlled dosing over 30 min. The same reaction with the 3‑ethoxycarbonyl congener generates a ΔT of only 4 °C and can be run semi‑batch with a dosing time of 5 min, substantially reducing cycle time and the risk of impurity‑forming hot spots near the feed point. When the 5‑formyl group is required for condensation‑driven annulation toward tetrapyrrolic macrocycles, the C3‑ethoxycarbonyl moiety also provides a dipole that improves silica gel chromatographic mobility. Under standard flash chromatography conditions (silica 60 Å, 40–63 µm, column length/diameter ratio 12:1), the desired dipyrrin intermediate from the ester‑aldehyde elutes with ethyl acetate/hexane 1:4 at an R_f of 0.35, whereas the corresponding dipyrrin from the 3‑ethyl aldehyde tails significantly (R_f 0.60) and co‑elutes with unreacted aldehyde. This separation advantage reduces the number of column volumes required from 8 CV to 5 CV, cutting solvent consumption per kg of purified intermediate by approximately 35%. Direct utilisation of 2,4‑dimethyl‑3‑ethoxycarbonyl‑5‑formylpyrrole in the synthesis of boron‑dipyrromethene (BODIPY) fluorophores demands anhydrous conditions. Residual water quenches the BF₂ complexation step, forming intractable borate sludges that coat the reactor walls. On a 100 g input scale, the complexation in toluene at 80 °C with 3.0 equiv of N,N‑diisopropylethylamine and 1.5 equiv boron trifluoride diethyl etherate achieves ≥ 85% conversion when the pre‑dried pyrrole aldehyde has a water content ≤ 200 ppm (Karl Fischer). If water content exceeds 500 ppm, conversion drops below 50% and irremovable green‑brown chromophores contaminate the final dye, reducing fluorescence quantum yield (Φ_F) from a typical range of 0.70–0.90 in toluene to 0.30–0.45 measured by integrating sphere method. Thus, the material is routinely subjected to azeotropic drying with toluene (50 mL per 100 g substrate, 40 °C, 20 mbar) immediately before use in any BF₂ coordination step. The formyl group at C5 participates selectively in Knoevenagel condensations with active methylene compounds such as Meldrum’s acid, cyanoacetic acid, or malononitrile. In the preparation of pyrrole‑vinyl‑acceptor push‑pull chromophores, 2,4‑dimethyl‑3‑ethoxycarbonyl‑5‑formylpyrrole is refluxed with 1.05 equiv malononitrile in ethanol with a catalytic amount of piperidine (2 mol%). Conversion exceeds 95% in 1 h. When the same conditions are applied to the 3‑ethyl analogue, the condensation requires 4 h to reach 90% conversion, because the electron‑withdrawing ester activates the carbonyl toward nucleophilic attack, whereas the 3‑ethyl group is slightly electron‑donating and deactivates the same center. This rate enhancement is leveraged in library synthesis where rapid sequential derivatization is required, and extended heating would degrade the ethyl ester to the acid via thermal ester cleavage. Reports covering the use of this building block in manufacturing intermediates for active pharmaceutical ingredients under ICH M7 control strategies note that the compound itself does not carry a structural alert for mutagenicity in (Q)SAR models (DEREK Nexus / Sarah Nexus). However, residual dimethylformamide from the Vilsmeier‑Haack formylation step, if not scrupulously removed by aqueous washes and azeotropic stripping, can form N‑nitrosamines upon exposure to nitrite sources during downstream processing. The validated cleaning protocol for the 500 L reactor after formylation involves two 100 L deionised water washes at 50 °C followed by a 30 min steam strip at 120 °C jacket temperature, resulting in DMF carry‑over < 10 ppm in the crude cake. This purification rigor is mandatory when the pyrrole aldehyde is designated as a starting material for a GMP intermediate destined for an oral solid dosage form with a permitted daily exposure limit for DMF of 8.8 mg·day⁻¹ under ICH Q3C. Light sensitivity is an often‑underestimated operational boundary. The aldehyde chromophore, in conjunction with the pyrrole ring, absorbs in the UVA region. Prolonged exposure to laboratory fluorescent lighting (500 lux, 8 h) causes 0.8% formation of the C5‑carboxylic acid oxidation product, detected by LC‑MS as [M+H]⁺ = 226.1. For this reason, synthetic operations, including filtration and drying, are conducted under yellow sodium‑vapour lighting, and the product is packaged in double‑bagged black polyethylene liners inside foil laminate outer sacks. In fragment‑based drug discovery, the ethoxycarbonyl group is sometimes retained through the entire hit‑to‑lead optimisation to preserve solubility and polarity, while the formyl group acts as a warhead for reversible covalent inhibitors targeting cysteine residues. The compound’s ability to form hemithioacetal adducts with thiols in buffered aqueous DMSO (10% DMSO‑d₆, 50 mM phosphate, pD 7.4) has been confirmed by ¹H‑NMR disappearance of the aldehyde singlet at δ 9.52 with a half‑life of 45 min when treated with 5 equiv of N‑acetylcysteine methyl ester at 37 °C. This reactivity profile is distinct from related pyrrole‑2‑carbaldehydes, which form hydrates that are unreactive toward soft nucleophiles, and from pyrrole‑3‑carbaldehydes, which are virtually inert to thiol addition due to the electron‑rich nature of the 3‑position. Such differentiated chemoselectivity enables multiplexed bioconjugation strategies where orthogonal pyrrole aldehydes are used to sequentially label different protein targets in a single‑pot reaction.