4-Ethyl-3-Methyl-5-Oxo-N-(2-Phenylethyl)-2H-Pyrrole-1-Carboxamide

Within current Good Manufacturing Practice (cGMP) synthesis campaigns targeting 5-HT₂ₐ receptor antagonists, 4-Ethyl-3-Methyl-5-Oxo-N-(2-Phenylethyl)-2H-Pyrrole-1-Carboxamide serves as a late-stage intermediate requiring hydrogenolytic cleavage of the phenethyl amide under strictly controlled volumetric mass transfer conditions. The process employs a 5% Pd/C catalyst (Johnson Matthey 5R39 or equivalent, 50–70% water-wet to mitigate pyrophoric risk) at a loading of 0.15–0.25 mol% Pd relative to substrate. The reaction is conducted in a 2.5:1 (v/v) tetrahydrofuran/2-propanol mixture at an internal temperature of 22–28°C, with hydrogen gas maintained at 1.5–2.8 bar(g) inside a 316L stainless-steel Parr reactor equipped with a gas-entrainment impeller operating at 800–1,100 rpm. In-line process analytical technology (PAT) employing ReactIR 45P with a diamond ATR probe monitors the disappearance of the carbonyl absorption at 1,685 cm⁻¹ (amide I band) to determine endpoint. Content of residual phenethylamine is controlled below 0.10 area% by HPLC per USP 621 prior to filtration through a 0.5-micron sintered metal candle filter, followed by solvent swap to ethyl acetate and crystallization from n-heptane at a cooling ramp of −0.3°C/min to afford the deprotected pyrrolidinone as a white crystalline solid with a typical melting onset of 96.8–98.2°C by DSC (ASTM E967). Residual palladium is controlled to ≤5 ppm as determined by ICP-MS following acid digestion, in alignment with ICH Q3D Step 4 elemental impurity guidelines for parenteral drug substances. Any deviation from the prescribed hydrogenation temperature window exceeding +5°C leads to pyrrole ring saturation and formation of the undesired ethyl-methyl-pyrrolidine byproduct, which co-elutes with the active compound under typical C18 reverse-phase conditions unless a pentafluorophenyl (PFP) stationary phase is substituted.

When 4-Ethyl-3-Methyl-5-Oxo-N-Phenethyl-2-Pyrroline-1-Carboxamide Enters Insecticide Intermediate Manufacturing under OECD GLP 13

Incorporation of the pyrrole carboxamide as a building block in the synthesis of phenylpyrazole acaricides follows a Knoevenagel-type condensation with ethyl 4,4,4-trifluoro-3-oxobutanoate in the presence of piperidinium acetate catalyst. The stoichiometry is fixed at 1.05 equivalents of the trifluoroacetoacetate ester relative to the amide, dissolved in toluene (8 L per kg substrate) and refluxed under a Dean-Stark trap until calculated water removal of 1.0 equivalents is achieved. This step generates the corresponding enaminoketone, which is directly treated with methylhydrazine (1.2 eq) at 5–10°C under nitrogen pad, followed by a controlled exotherm to 80°C over 4 hours to effect cyclization. The resulting trifluoromethylpyrazole intermediate is isolated by drowning into ice-water and recrystallized from aqueous ethanol to reach a purity specification of ≥98.5% by GC-FID (column: DB-5, 30 m × 0.25 mm, film 0.25 µm). Process validation requires verification of absence of genotoxic hydrazine residues at a limit of ≤1 µg/g using a derivatized HPLC-UV method with pre-column benzaldehyde treatment, consistent with the ALARP principle under EMA/CHMP/SWP/2010/026849. The final acaricide product derived from this intermediate exhibits contact activity against Tetranychus urticae with an LC₉₀ of 12–18 g a.i./hL in field trials, but published data correlating this specific carboxamide with field performance is limited; bioefficacy linkage remains inferred from structure-activity relationships of the trifluoromethylpyrazole class. Key processing hazard: the condensation step releases exothermic energy of approximately −120 kJ/mol; reactor cooling capacity must be rated for a ΔT_ad of ≤40°C under loss of stirring scenario per RC1e adiabatic calorimetry characterization.

What drives the compound’s utility as a heterocyclic scaffold for triazole-based fungicide actives?

Conversion of the carboxamide into a 1,2,4-triazole-3-thione pharmacophore proceeds via a three-step sequence initiated by amide activation with phosphorus oxychloride (1.3 eq) in dichloroethane at 50°C to form the intermediate chloroiminium species. This is immediately quenched with anhydrous hydrazine (2.0 eq) supplied as a 35% solution in THF at −10 to −5°C, producing the corresponding amidrazone hydrochloric acid salt. Subsequent ring closure with carbon disulfide (1.5 eq) and potassium hydroxide (2.1 eq) in refluxing ethanol yields the 5-mercapto-1,2,4-triazole nucleus, which is S-alkylated with 2-chloromethyl-5-ethoxy-1,3,4-thiadiazole (1.0 eq) in acetone using potassium carbonate as base. The final active ingredient is a systemic triazole-thioether exhibiting CYP51 inhibition, with EC₅₀ values typically in the sub-micromolar range against Zymoseptoria tritici. Residual solvent compliance is enforced per USP 467 (Class 1/2/3 limits); particular attention is directed at dichloroethane carry-over, which must not exceed 5 ppm in the active material intended for EU registration under Regulation (EC) 396/2005. Process-scale centrifugation of the amidrazone intermediate requires Hastelloy C-276 wetted parts to withstand the acidic chloride environment; failure to maintain pH below 3 during salt formation leads to premature cyclization and gumming of the centrifuge basket. Acaricidal and fungicidal final formulations typically combine the triazole active at 100–250 g/L as an emulsifiable concentrate (EC) with aromatic solvent naphtha (CAS 64742-94-5) and an anionic/nonionic surfactant package comprising calcium dodecylbenzenesulfonate and tristyrylphenol ethoxylate (HLB 11.5–13.0).

Development of a semisynthetic metalworking fluid (MWF) corrosion inhibitor package integrates 4-Ethyl-3-Methyl-5-Oxo-N-(2-Phenylethyl)-2H-Pyrrole-1-Carboxamide at 0.8–1.5 wt% into a hydrocarbon base oil (Group II, 40°C KV 12–15 cSt) emulsified with sodium petroleum sulfonate (8–12 wt%) and tall oil fatty acid diethanolamide. Copper corrosion inhibition performance is evaluated per ASTM D130 (IP 154) at 100°C for 3 hours; the pyrrole carboxamide additive maintains a 1a/1b rating when the formulation ratio of boron to nitrogen (from amide functionality) is kept between 0.35 and 0.55 on a molar basis. Outside this window—particularly when boron overbase from potassium borate exceeds 0.60 molar ratio—copper staining shifts to 2c and ferrous corrosion as per ASTM D665 Procedure A (distilled water) exhibits visible rusting beyond 6 hours of test duration. Tribological behavior is characterized on a Bruker UMT TriboLab using a 52100 steel ball-on-disc configuration: at 25°C, 50 N load, 50 Hz, the addition of 1.2 wt% of the compound reduces the coefficient of friction from 0.122 to 0.087 and enlarges the weld load capacity from 1,600 N to 2,200 N in a Falex pin-and-vee test (ASTM D3233). Compatibility with polyacrylate and polymethacrylate viscosity modifiers is critical; introduction of the amide-containing inhibitor into formulations with >5 wt% PMMA pour point depressant (MW 25,000) results in demulsification after 48 hours of static storage at 40°C unless a nonionic EO/PO block copolymer (HLB 9–10) is co-added at triple the amide concentration. The exact mechanism of corrosion mitigation is attributed to chemisorption of the carbonyl and π-electron system of the pyrrole ring onto the metal surface, as indicated by XPS spectra showing N 1s peak broadening at binding energies of 399.8 eV (amine-like) and 401.5 eV (quaternary ammonium-like) after immersion of copper coupons in the inhibited fluid. REACH registration documentation for this application commonly references the DU sector for lubricants (use descriptor SU17, PROC1, PROC2, ERC4).

Photoresist PAG precursor synthesis demands sub-ppb metal contamination control in Class 100 cleanroom environments

In EUV and DUV photoresist formulations for semiconductor manufacturing at sub-7 nm nodes, 4-Ethyl-3-Methyl-5-Oxo-N-(2-Phenylethyl)-2H-Pyrrole-1-Carboxamide is converted into a photoacid generator (PAG) via sulfonation with 1.2 equivalents of perfluorobutane sulfonyl fluoride in anhydrous dichloromethane containing triethylamine (1.5 eq) at 0–5°C under dry nitrogen. After aqueous work-up, the crude sulfonamide PAG is purified through a three-step process: charcoal treatment (Norit SX-Plus, 2% w/w) to adsorb organic impurities, filtration through a 0.1 µm PTFE membrane, and final crystallization from a 3:7 (v/v) mixture of ethyl acetate and cyclohexane, yielding a product with total trace metals below 10 ppb as measured by ICP-MS (Fe, Cr, Ni, Na, K, Ca each ≤1 ppb). The PAG is air-classified in a Nutsche filter-dryer inside an ISO 3 (Class 1) cleanroom, with particle count verified per IEST-RP-CC034 to ensure no particles ≥0.2 µm. Lithographic evaluation uses an ASML Twinscan NXE:3400C scanner; a photoresist comprised of polyhydroxystyrene-based resin, 20 wt% of the synthesized PAG, and 1.2 wt% quencher base (triethanolamine) in cyclohexanone achieves a line/space resolution of 13 nm half-pitch at a dose of 34 mJ/cm² under dipole illumination (σ 0.3/0.7). Outgassing behavior under high-vacuum EUV exposure (base pressure 1×10⁻⁷ mbar) is assessed via residual gas analyzer (RGA) following SEMI F47 guidelines; total outgassed hydrocarbons must remain ≤1.0×10⁻¹² g/cm² to prevent contamination of collector optics. Compatibility with standard developer (tetramethylammonium hydroxide 2.38%) is confirmed by immersion development at 23°C for 60 seconds, giving a contrast ratio of 4.8. The compound’s stability in resist solution is limited; after 7 days at 5°C, PAG degradation of 0.8–1.2% is observed by ¹⁹F NMR, necessitating cold-chain storage and point-of-use mixing in the track line.

In two-component polyurethane elastomer castings for mining screen applications, the carboxamide acts as a latent catalyst synthon that is pre-reacted with a substoichiometric quantity of hexamethylene diisocyanate trimer (Desmodur N 3600) to form a blocked prepolymer. The blocking mechanism exploits the N‒H acidity of the amide group; the prepolymer is blended into the polyether polyol component (Voranol 2000, OH value 56 mg KOH/g) at a loading delivering 0.12–0.18 equivalents of blocked NCO relative to total formulated OH groups. Pot life at 40°C extends from a baseline of 18 minutes (unblocked) to 52 minutes, measured until dynamic viscosity reaches 10,000 mPa·s on a Brookfield RVDV-E viscometer (spindle 27, 20 rpm). Deblocking initiates above 90°C, leading to a fast gel time of 4–5 minutes thereafter; the resulting elastomer exhibits Shore A hardness of 85–90 (DIN 53505), tear strength of 38 kN/m (DIN ISO 34-1, Die C), and Taber abrasion loss below 45 mg/1,000 cycles (H-22 wheel, 1 kg, ASTM D4060). A critical processing limitation is the moisture sensitivity of the blocked adduct: at ambient relative humidity >55%, the prepolymer hydrolyzes over 8 hours, releasing free NCO species and generating carbon dioxide, which causes micro-porosity in the final casting. Therefore, all handling of the prepolymerized intermediate is performed under a dry nitrogen blanket and packed in moisture-impermeable aluminum-lined composite drums. Compliance with the 1935/2004 EC framework for food-contact materials is not achievable for this compound due to the pyrrole moiety’s migration behavior, and its use is excluded from any indirect food additive applications.