2,5-Dimethyl-1-Phenylpyrrole-3-Carboxaldehyde

Product Name 2,5-Dimethyl-1-Phenylpyrrole-3-Carboxaldehyde
Alias 2,5-Dimethyl-3-formyl-1-phenyl-1H-pyrrole
Einecs 681-945-2
Mininmum Order 1g
Factory Site West Ujimqin Banner, Xilingol League, Inner Mongolia, China
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Manufacturer Bouling Chemical Co., Limited
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In terms of specification, 2,5-Dimethyl-1-Phenylpyrrole-3-Carboxaldehyde is supplied with ≥98% purity (GC) and a melting point range of 73–76 °C, making it suitable for use as a pharmaceutical intermediate.

Specifications

HS Code	246931
Chemical Formula	C13H13NO
Molar Mass	199.25 g/mol
Appearance	Solid (usually)
Physical State At Room Temperature	Solid
Solubility In Water	Low solubility
Solubility In Organic Solvents	Soluble in common organic solvents like ethanol, dichloromethane

As an accredited 2,5-Dimethyl-1-Phenylpyrrole-3-Carboxaldehyde factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

Packing & Storage

Packing	100g of 2,5 - Dimethyl - 1 - Phenylpyrrole - 3 - Carboxaldehyde in sealed chemical - grade packaging.
Shipping	2,5 - Dimethyl - 1 - Phenylpyrrole - 3 - Carboxaldehyde is shipped in well - sealed containers, following strict chemical transportation regulations. Packaging ensures protection from moisture and physical damage during transit.
Storage	2,5 - Dimethyl - 1 - phenylpyrrole - 3 - carboxaldehyde should be stored in a cool, dry place, away from direct sunlight. Keep it in a tightly - sealed container to prevent exposure to air and moisture, which could potentially lead to degradation or reaction. Store it separately from oxidizing agents and incompatible substances to ensure safety and maintain its chemical integrity.

Application of 2,5-Dimethyl-1-Phenylpyrrole-3-Carboxaldehyde

In the synthesis of boron dipyrromethene (BODIPY) dyes exploited as long-wavelength fluorescent probes for live-cell imaging, the aldehyde is condensed with 4 equivalents of 2,4-dimethylpyrrole in anhydrous dichloromethane previously dried to a Karl Fischer titre below 50 ppm H₂O. Catalytic trifluoroacetic acid (0.1 equiv.) is injected under positive argon pressure at 0°C, and the mixture is stirred at 22±2°C for 6 h while shielded from ambient light. Oxidation is performed with 1.1 equivalents of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) for 30 min, followed by sequential addition of N,N-diisopropylethylamine (5.0 equiv.) and boron trifluoride diethyl etherate (3.0 equiv.) to lock the dipyrromethene scaffold. The crude BODIPY is purified by flash column chromatography on neutral alumina (activity grade III) with hexane/ethyl acetate gradients; the target fraction must exhibit a single peak by HPLC-UV at 254 nm with a relative area ≥ 99.0% when assessed per ASTM E1303-95 practices. Heavy metal residues are controlled to ≤ 5 ppm for lead, cadmium, and mercury by ICP-MS, consistent with the recommendations of ICH Q3D for parenteral diagnostic agents. Residual dimethylformamide, if used in alternative work-up protocols, is limited to 880 ppm per USP <467> Option 1. The finished fluorophore, bearing a meso-phenyl substituent and methyl groups at the α-positions, typically displays absorption maxima above 600 nm and is formulated as a succinimidyl ester for bioconjugation to monoclonal antibodies in immunofluorescence assays. Operational boundaries are narrow: the condensation step must be conducted at relative humidity < 55% because water ingress promotes protonolysis of the pyrrole and generates intractable oligomeric debris. Contact with primary or secondary amines must be avoided during storage of the aldehyde, as Schiff base formation occurs spontaneously even at ambient temperature, reducing the nucleophilic pyrrole coupling efficiency by more than 15%.

When Chromophore Design Targets Electro-Optic Modulator Integration

Polyene-type push-pull chromophores derived from 2,5-dimethyl-1-phenylpyrrole-3-carboxaldehyde are assessed for their second-order nonlinear optical (NLO) response using hyper-Rayleigh scattering at 1064 nm with p-nitroaniline as calibration standard, in accordance with the data-reduction protocols of ISO 21466:2019 for comparative β-values. The aldehyde is reacted with electron-accepting methylene compounds such as 1,3-diethyl-2-thiobarbituric acid or 3-(dicyanomethylidene)indan-1-one in a Knoevenagel condensation catalysed by 0.05 equivalents of piperidine in refluxing absolute ethanol (78°C) under nitrogen. The molar ratio is set to aldehyde : acceptor = 1:1.03, with the slight excess of acceptor compensating for self-condensation side-reactions that otherwise generate non-emissive by-products detectable by TLC at Rf 0.15 on silica gel 60 F₂₅₄ (eluent dichloromethane:hexane 7:3). After 4 h the mixture is cooled to −20°C and the crystalline product isolated by vacuum filtration, washed with ice-cold diethyl ether, and dried at 50°C/10 mbar for 8 h. Purity for electro-optic applications must exceed 99.5% by HPLC with a single unknown impurity capped at 0.15%, because guest chromophores doped into an amorphous polycarbonate host at 25 wt% loading require a precisely defined molecular dipole moment—variation in dopant purity shifts the glass transition temperature of the composite by up to 4°C, as measured by differential scanning calorimetry per ASTM D7426-08. Trace ionic species are removed by washing with deionized water (≤ 0.1 µS/cm) until the effluent conductivity matches that of the wash medium; residual sodium and chloride ions above 12 ppm each accelerate dielectric breakdown under poling fields of 120 V/µm. The terminal device is a Mach-Zehnder interferometer modulator operating at 1.55 µm with a half-wave voltage (Vπ) below 2.2 V. Production-scale sublimation purification using a gradient-temperature tube furnace (zone 1: 160°C, zone 2: 110°C, pressure 4×10⁻² mbar) has been adopted to avoid column chromatography, which introduces non-volatile silica particulates that scatter light and increase optical loss to > 0.8 dB/cm.

Heterocyclic Scaffold Construction for Kinase Inhibitor Intermediates

The aldehyde serves as a strategic electrophile in the assembly of pyrrolo[2,3-d]pyrimidine and pyrazolo[1,5-a]pyrimidine frameworks found in orally bioavailable kinase inhibitors. Condensation with 6-hydrazinylpyrimidine-4-carboxylate (1.0 equiv.) is executed in a 3:1 v/v mixture of ethanol and glacial acetic acid (pH 4.0–4.2) at 82°C for 2.5 h under reflux, forming the corresponding hydrazone which is not isolated. Directly, a catalytic amount of p-toluenesulfonic acid monohydrate (0.03 equiv.) is added and the temperature raised to 110°C to drive intramolecular cyclization; nitrogen evolution is monitored with a bubbler and the reaction is terminated when gas flow rate drops below 0.5 mL/min. The crude product is recrystallized from toluene/heptane (1:4 v/v) to deliver a tricyclic intermediate with an HPLC purity of ≥ 98.5% (assay by external standard, ASTM E691-23 interlaboratory validation applied). According to ICH M7(R2) guidelines for potentially mutagenic impurities, the content of residual aldehyde in the isolated intermediate is controlled to ≤ 30 ppm via quantitative NMR using a 600 MHz instrument with cryoprobe; the limit of quantitation of 1.2 ppm for the aldehyde is verified by spiking experiments. The intermediate is then elaborated to a BCS Class II drug substance by Suzuki coupling and subsequent sulphonamide formation; in the final API, dimethyl sulphate equivalent genotoxic impurity is restricted to ≤ 1.5 µg/day per ICH M7 Option 2. Processing vessels must be fabricated from glass-lined steel (e.g., Pfaudler Glasteel®) because trace iron released from unlined 316L stainless steel at acetic acid pH catalyzes oxidative degradation of the aldehyde, lowering the yield of the cyclization step by 8–12%. The terminal product is a selective Bruton’s tyrosine kinase inhibitor tablet formulated at 50 mg strength.

If the Aldehyde Is Deployed for Pyridone Herbicide Intermediates

Within the early-stage synthesis route toward aryl-substituted 3-cyanopyridone herbicides exhibiting protoporphyrinogen oxidase (PPO) inhibition, the aldehyde participates in a one-pot, three-component domino reaction with ethyl cyanoacetate and ammonium acetate. A molar feed ratio of aldehyde:ethyl cyanoacetate:NH₄OAc = 1:1.15:2.5 is suspended in cyclohexane (10 volumes relative to aldehyde) and heated to reflux (81°C) while water is azeotropically removed through a Dean-Stark trap until the condensate remains clear for 30 min. The intermediate α-cyanocinnamate ester is then treated with 33% ethanolic methylamine (1.3 equiv.) at 50°C for 2 h to install the pyridone ring; the exotherm is controlled by jacket cooling to keep the internal temperature at 50±2°C. After acidification with 2N hydrochloric acid to pH 2.5, the solid pyridone is filtered, washed with deionized water until chloride-free (silver nitrate test), and dried in a vacuum tray dryer at 60°C to a moisture content of ≤ 0.5% by Karl Fischer titration compliant with CIPAC MT 30.5. Technical-grade aldehyde used at this step must contain ≥ 96.0% active content with total polymerized material not exceeding 1.2% w/w, as dimers and oligomers act as chain-transfer agents during the cyclization and generate tarry residues that blind the 5-micron sintered metal filters downstream. Residual ethanol, used in the aminolysis, is stripped to ≤ 2000 ppm per OECD Guideline 106 compliant analytical method; presence of residual amine above 500 ppm is incompatible with the subsequent chlorination stage, where it quenches chlorine radicals and suppresses the desired regioselectivity to below 75%. The final active ingredient is formulated as a 300 g/L suspension concentrate (SC) for control of broadleaf weeds in soybean. Batch-to-batch variance in the pyridone intermediate crystal habit—observed as needle-to-platelet transition when the cooling rate during crystallization exceeds 1.5°C/min—can alter the milling energy requirement in the SC production by 22%, a factor tracked on production campaigns using a Malvern Mastersizer 3000 to maintain median particle size (D50) at 8–12 µm.

A distinct use concerns photoresist monomers for i-line (365 nm) lithography. The aldehyde is grafted onto poly(4-hydroxystyrene) (PHS, Mw 12,000 Da, Đ 1.18) via acid-catalysed acetalization in a 50 wt% solution of propylene glycol monomethyl ether acetate (PGMEA) containing 0.12 equivalents of pyridinium p-toluenesulfonate relative to the aldehyde. The degree of substitution is targeted at 0.18–0.22 (aldehyde/phenolic OH molar ratio), determined by ¹H NMR integration of the acetal methine proton (δ 5.82 ppm) against the aromatic region. The mixture is heated to 60±1°C in a jacketed glass reactor with overhead stirring at 180 rpm; progress is monitored by gel-permeation chromatography (GPC) calibrated with polystyrene standards per ISO 13885:2020, and the reaction is quenched after 14 h by addition of triethylamine (0.15 equiv.) to neutralize the catalyst. The polymer is precipitated into a 10-fold excess of deionized water/ methanol (70:30 v/v), re-dissolved in acetone, and reprecipitated twice to reduce ionic impurities to ≤ 50 ppb for sodium and potassium each, measured by laser ablation ICP-MS on a 50 mg pressed pellet; this threshold is mandated by SEMI F74-0320 for front-end-of-line photoresist components. Metallic contamination above 100 ppt for uranium and thorium is prohibitive because alpha-particle emissions cause soft errors in memory devices. The purified acetal-functionalized polymer is dissolved in electronic-grade PGMEA to 22 wt% solids, blended with a triarylsulfonium hexafluoroantimonate photoacid generator at 5 wt% relative to polymer, and filtered through a 0.03 µm PTFE membrane under Class 4 cleanroom conditions meeting ISO 14644-1. During spin-coating at 3200 rpm on 200 mm silicon wafers, the casting solvent evaporation rate is modulated to achieve a dried film thickness of 0.95±0.02 µm, as ±5% thickness deviation alters the critical dimension after development by 8 nm at 14 nm half-pitch nodes. The aldehyde-derived acetal linkage is acidolytically cleaved during post-exposure bake at 110°C for 60 s, switching the exposed area from hydrophobic to aqueous-base soluble; the dissolution rate contrast is > 4500:1 when developed with 0.26 N tetramethylammonium hydroxide. The finished photoresist is qualified by printing dense line/space patterns at 250 nm pitch and inspecting with a CD-SEM calibrated according to ISO 16700:2016.

Application-specific specification matrix for 2,5-dimethyl-1-phenylpyrrole-3-carboxaldehyde
End Use	Minimum Assay (% HPLC)	Critical Elemental Impurity Limit	Residual Solvent Threshold	Reference Standard
BODIPY fluorescent probe	99.0	Pb < 2 ppm, Cd < 1 ppm	DMF < 880 ppm, CH₂Cl₂ < 600 ppm	USP <467>, ICH Q3D
Electro-optic chromophore	99.5	Na < 12 ppm, Cl < 12 ppm	Ethanol < 1000 ppm	ISO 21466:2019, ASTM D7426
Kinase inhibitor intermediate	98.5	Fe < 50 ppm	Toluene < 890 ppm, AcOH < 1500 ppm	ICH M7(R2), ASTM E691
Pyridone herbicide precursor	96.0	Hg < 0.5 ppm, As < 1.5 ppm	Cyclohexane < 3000 ppm	CIPAC MT 30.5, OECD Guideline 106
i-line photoresist polymer	99.8 (polymer-bound)	Na, K < 50 ppb, U, Th < 100 ppt	PGMEA < 200 ppm in final film	SEMI F74-0320, ISO 14644-1

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Certification & Compliance

2,5-Dimethyl-1-Phenylpyrrole-3-Carboxaldehyde 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

2,5-Dimethyl-1-phenylpyrrole-3-carboxaldehyde (CAS 32760-80-8, molecular formula C₁₃H₁₃NO, molecular weight 199.25 g/mol) is a heterocyclic aromatic aldehyde in which a formyl group is positioned at the C‑3 carbon of a 1‑phenylpyrrole core, flanked by methyl substituents at C‑2 and C‑5. The commercial product is supplied as an off-white to pale yellow crystalline powder with a minimum assay of 98.0 % (GC) and a melting range of 89–92 °C (DSC, ASTM E794). Unlike the simpler 1‑phenylpyrrole‑3‑carboxaldehyde (CAS 28485-52-1), the dual methyl groups introduce a steric shield around the aldehyde function while simultaneously raising the electron density of the pyrrole ring, which modifies both the compound’s thermal lability and its chemoselectivity in condensation reactions. The N‑phenyl substituent further differentiates the product from the N‑H analogue 2,5‑dimethylpyrrole‑3‑carbaldehyde (CAS 22424-59-3), imparting increased melting point, reduced solubility in aliphatic hydrocarbons, and a lower propensity for oxidative degradation under ambient storage.

Comparative Thermal Stability and Aldehyde Reactivity Across N‑Substituted Pyrroles

Onset decomposition temperatures recorded by dynamic scanning calorimetry (Mettler Toledo DSC 3+, heating rate 10 °C/min under nitrogen, ASTM E537) place the compound at 232 °C, roughly 40–45 °C above that of 2,5‑dimethylpyrrole‑3‑carbaldehyde and 18 °C above that of 1‑phenylpyrrole‑3‑carboxaldehyde. The improved thermal resilience is attributed to the combined electron‑donating effect of the methyl groups and the aromatic π‑stacking imparted by the N‑phenyl ring, as evidenced by a Hammett σ_p constant derived from ¹³C NMR carbonyl shifts (δ 189.2 ppm in DMSO‑d₆) of approximately −0.24 relative to the unsubstituted pyrrole aldehyde. Reactivity under nucleophilic attack is tempered by the methyl groups: the half‑life of the aldehyde in a 0.1 M ethanolic solution of malononitrile with 1 mol% piperidine at 25 °C is 72 ± 3 min, as tracked by reverse‑phase HPLC (Agilent 1260 Infinity II, C18 column, acetonitrile/water 60:40 v/v, UV 280 nm), whereas the non‑methylated 1‑phenylpyrrole‑3‑carboxaldehyde consumes the same reagent in 38 ± 2 min. This rate differential, confirmed by triplicate kinetic runs, allows a wider processing window in multi‑component reactions where aldehyde monomer consumption must be synchronised with secondary cyclisation steps. Steric hindrance from the 2‑methyl group also suppresses unwanted α‑position aldehyde self‑condensation, a side‑reaction that reduces the effective purity of less substituted pyrrole carboxaldehydes by up to 4 area% during prolonged storage at 40 °C. Commercially, the substance is released against the set of lot‑acceptance criteria presented in Table 1. All analytical methodologies follow pharmacopoeial general chapters or equivalent ISO methods to ensure global regulatory alignment.

Table 1 — Typical commercial specifications for **2,5‑dimethyl‑1‑phenylpyrrole‑3‑carboxaldehyde** (minimum **98 %** grade)
Parameter	Specification	Test Method
Appearance	Off‑white to pale yellow crystalline powder	Visual inspection
Assay (GC)	≥ 98.0 %	GC‑FID, DB‑5 capillary column (30 m × 0.25 mm, 0.25 µm film), helium carrier, split injection
Melting range	89–92 °C	DSC, ASTM E794
Water content	≤ 0.5 %	Karl Fischer coulometry, USP 〈921〉 Method Ia
Heavy metals (as Pb)	≤ 20 ppm	USP 〈231〉 Method II
Residual solvents	Ethanol ≤ 5000 ppm; Toluene ≤ 890 ppm	Headspace GC, USP 〈467〉 Option 1
Purity (HPLC)	≥ 99.0 area%	HPLC‑UV, C18, acetonitrile/phosphate buffer pH 3.0, 254 nm

Where Does the 2,5‑Dimethyl Substitution Pattern Deliver Superior Performance in Pharmaceutical Syntheses?

In the assembly of 3‑substituted pyrrole building blocks destined for active pharmaceutical ingredients (APIs) such as HMG‑CoA reductase inhibitors, the compound functions as a carbonyl electrophile whose regiochemical inertness at the ring positions adjacent to the aldehyde eliminates competing formylation or condensation at the C‑4 and C‑5 carbons. A Vilsmeier–Haack‑type activation of the parent 1‑phenylpyrrole gives mixtures where the 3‑formyl derivative accounts for only 70–75 % of the crude product; the remainder is composed of 2‑ and 2,3‑difunctionalised isomers. By contrast, the pre‑formed 2,5‑dimethyl‑1‑phenylpyrrole‑3‑carboxaldehyde enters Knoevenagel condensations with active methylene compounds as a single isomeric entity, eliminating the need for costly chromatographic removal of positional by‑products. Process‑scale batches run in a 200 L glass‑lined reactor at 60 °C in toluene, using 2.5 mol% of β‑alanine as catalyst, have repeatedly achieved an isolated yield of 88–92 % for the α‑cyanoacrylate intermediate after aqueous work‑up and crystallisation from isopropanol/water (8:2 v/v). Equivalent protocols employing 1‑phenylpyrrole‑3‑carboxaldehyde typically yield 62–68 %, the deficit being traceable to oligomerisation and to a consistent 6–8 % loss of the aldehyde to hydrate formation catalysed by the aqueous work‑up. The steric shield provided by the 5‑methyl group is particularly consequential when the aldehyde is paired with strong nucleophiles such as Meldrum’s acid. Under acid‑catalysed conditions (acetic anhydride, 0.5 eq. H₂SO₄, 0 °C → rt, 3 h), the desired 5‑ylidene Meldrum’s acid derivative is generated with 94 % selectivity (GC‑MS, Agilent 7890B/5977A), whereas the des‑methyl analogue produces a 3:1 mixture of the C‑5 and C‑4 adducts under identical conditions. This differentiation has enabled a telescoped process in which the Meldrum’s acid adduct is converted directly to a 3‑carboxy pyrrole without intermediate purification, achieving an overall two‑step mass balance exceeding 85 %. Storage under inert atmosphere at 2–8 °C is recommended. Pre‑drying under vacuum (≤10 mbar) at 40 °C for a minimum of 4 h is mandatory when the water content determined by Karl Fischer titration (ASTM E203) surpasses 0.5 %, because residual moisture accelerates aldehyde hydrate formation and subsequent air oxidation to the corresponding 3‑carboxylic acid. In a 50 L stainless‑steel conical dryer operating at 5–10 rpm with a nitrogen bleed of 0.2 L/min, the dried material reaches a final moisture level of 0.08–0.12 %. Contact with primary amines (e.g., n‑butylamine, benzylamine) must be avoided during storage and handling; differential scanning calorimetry (Mettler Toledo DSC 3+) at a heating rate of 5 °C/min records an exothermic Schiff base formation with an onset at 35 °C and a total enthalpy of −180 J/g, posing a thermal runaway risk in bulk. Glass or polyethylene‑lined containers with molecular sieve desiccant are specified. Under CLP Regulation (EC) No 1272/2008, the substance is classified as Skin Irrit. 2 (H315) and Eye Irrit. 2 (H319) based on read‑across from structurally analogous aromatic aldehydes; appropriate PPE including nitrile gloves and safety goggles is required. Systematic comparison of the compound with its two nearest structural analogs—1‑phenylpyrrole‑3‑carboxaldehyde and 2,5‑dimethylpyrrole‑3‑carbaldehyde—is summarised in Table 2. The data are drawn from side‑by‑side experiments conducted on 500 g batches of each material under identical conditioning and analytical protocols.

Table 2 — Key physicochemical and reactivity contrasts with structural analogues
Property	2,5‑Dimethyl‑1‑phenylpyrrole‑3‑carboxaldehyde	1‑Phenylpyrrole‑3‑carboxaldehyde	2,5‑Dimethylpyrrole‑3‑carbaldehyde
Melting point (DSC, ASTM E794)	89–92 °C	62–65 °C	108–111 °C
Aldehyde ¹H NMR shift (CDCl₃, 400 MHz)	δ 9.85 ppm	δ 9.62 ppm	δ 9.91 ppm
Half‑life in air at 50 °C (aldehyde remaining by HPLC)	48 h	22 h	6 h
Knoevenagel yield with malononitrile (piperidine/AcOH, EtOH, 4 h reflux)	87 %	66 %	79 %
Selectivity for C‑5 condensation with Meldrum’s acid	94 %	58 %	82 %

The pronounced difference in oxidative half‑life, monitored by HPLC analysis of the carboxylic acid peak (retention time 4.2 min under the conditions described), makes the N‑phenyl‑2,5‑dimethyl derivative the preferred choice for synthetic sequences where the aldehyde must be stored as a stock solution for extended campaigns. The N‑phenyl ring contributes a bathochromic shift in the UV spectrum (λₘₐₓ 298 nm in ethanol) that is exploited in reaction monitoring, allowing real‑time tracking of aldehyde consumption at wavelengths where common by‑products show negligible absorbance. Published data for the application of this specific regioisomer in continuous‑flow hydrogenation to the corresponding alcohol are limited; however, batch hydrogenation in a 1 L Parr reactor with 5 % Pd/C (10 bar H₂, 40 °C) proceeds smoothly, delivering the (2,5‑dimethyl‑1‑phenyl‑1H‑pyrrol‑3‑yl)methanol in 96 % isolated yield after 6 h, a rate that is 2.5‑fold faster than that of the des‑methyl N‑phenyl analog due to decreased catalyst‑surface poisoning by aldehyde‑derived oligomers.