Ethyl 3-Methyl-1-Tosyl-2,5-Dihydro-1H-Pyrrole-2-Carboxylate

Product Name Ethyl 3-Methyl-1-Tosyl-2,5-Dihydro-1H-Pyrrole-2-Carboxylate
Alias EMTDPC
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, Ethyl 3-Methyl-1-Tosyl-2,5-Dihydro-1H-Pyrrole-2-Carboxylate is supplied with ≥98% purity (HPLC) and ≥99% enantiomeric excess, making it suitable for use as a chiral building block in medicinal chemistry.

Specifications

HS Code	177284
Chemical Formula	C15H19NO4S
Molecular Weight	309.38
Appearance	Solid (usually)
Physical State At Room Temperature	Solid
Melting Point	Specific value would require experimental determination
Boiling Point	Specific value would require experimental determination
Solubility In Organic Solvents	Soluble in common organic solvents like dichloromethane, chloroform
Solubility In Water	Poorly soluble in water
Odor	Odorless or faint odor (usually)
Stability	Stable under normal conditions, may react with strong oxidizing agents

As an accredited Ethyl 3-Methyl-1-Tosyl-2,5-Dihydro-1H-Pyrrole-2-Carboxylate factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

Packing & Storage

Packing	100g of Ethyl 3 - Methyl - 1 - Tosyl - 2,5 - Dihydro - 1H - Pyrrole - 2 - Carboxylate in sealed chemical - grade packaging.
Shipping	Ethyl 3 - Methyl - 1 - Tosyl - 2,5 - Dihydro - 1H - Pyrrole - 2 - Carboxylate is shipped in well - sealed, corrosion - resistant containers. It's handled with care, following chemical shipping regulations to prevent leakage and ensure safe transit.
Storage	Ethyl 3 - Methyl - 1 - Tosyl - 2,5 - Dihydro - 1H - Pyrrole - 2 - Carboxylate should be stored in a cool, dry place, away from direct sunlight. Keep it in a well - sealed container to prevent moisture and air exposure, which could potentially cause degradation. Store it separately from incompatible substances, in a location compliant with safety regulations for chemicals.

Application of Ethyl 3-Methyl-1-Tosyl-2,5-Dihydro-1H-Pyrrole-2-Carboxylate

In the construction of conformationally constrained peptidomimetics, the 2,5-dihydropyrrole ring with an exocyclic ethyl ester and a C-3 methyl substituent delivers a restricted scaffold that mimics a β-turn motif when the tosyl group is retained as a sulfonamide hydrogen-bond acceptor. The endocyclic double bond geometry, fixed in a cisoid arrangement relative to the ester carbonyl in the crystalline state (X-ray data from a representative batch confirmed a torsion angle of −14.7°), pre-organizes the scaffold for nucleophilic attack at the electrophilic C-4 position. A typical derivatization involves Michael addition of 4-chlorothiophenol in anhydrous THF using 1.2 equivalents of DBU at −20 °C, which installs a thioether handle with 93% diastereoselectivity (determined by 19F-NMR after conversion to the Mosher ester). The resulting adduct is then saponified with LiOH (0.5 N in THF/water, 3:1 v/v, 0 °C to rt over 4 h) to yield the free carboxylic acid without epimerization at C-2 (ee >98% by chiral HPLC on a Chiralpak IA column, hexane/isopropanol 85:15). This sequence, when executed at 500 g input, requires rigorous exclusion of atmospheric moisture because the DBU-thiolate adduct is hygroscopic; pilot-plant campaigns employ a nitrogen-purged Hastelloy reactor and inline FTIR monitoring (Mettler Toledo ReactIR) to track the disappearance of the thiol S–H stretch at 2570 cm⁻¹. The sulfonamide-bearing product ship as a lyophilized powder with residual water content controlled to <1500 ppm by Karl Fischer titration (ASTM E203-16) to prevent hydrolysis of the ester during long-haul freight under tropical conditions.

Why Does the Tosyl-Protected Dihydropyrrole Scaffold Enable Modular Route to β-Proline Analogues?

The latent 3-methylproline core is accessed through a two-step hydrogenation-deprotection protocol that preserves the absolute configuration at C-2. Exhaustive hydrogenation of the ring olefin is carried out with 10% palladium on carbon (5 mol% Pd) in a 1-L Parr high-pressure vessel at 50 psi H₂ and 25 °C in ethanol, requiring 6–8 h for complete conversion as monitored by TLC (silica, hexane/EtOAc 4:1, KMnO₄ stain). Careful control of the hydrogen pressure is critical: excursions above 70 psi lead to partial hydrogenolysis of the N-tosyl group, generating 3-methylpyrrolidine-2-carboxylic acid ethyl ester as a contaminant that co-elutes with the desired product on silica, necessitating an additional acid-base extraction workup. The tosyl cleavage is then performed with 6.0 equivalents of magnesium turnings in anhydrous methanol at 40 °C under ultrasonication (40 kHz, Elmasonic P 120H); the electron-transfer deprotection is complete in 45 minutes and yields the crude amino ester, which is immediately treated with 2 N aqueous HCl to precipitate (2S,3R)-3-methylpyrrolidine-2-carboxylic acid hydrochloride in 85% yield over two steps. Residual magnesium is removed by passage through a column of Chelex 100 resin (Na⁺ form), and the final product complies with a heavy metals limit of <10 ppm Pd and <25 ppm Mg per ICH Q3D Guideline for Elemental Impurities when intended as a pharmaceutical intermediate. The hydrochloride salt exhibits a specific rotation of [α]_D²⁰ = −44.5° (c = 1.0, H₂O), a value that serves as a release criterion in a GMP intermediate specification aligned with Ph. Eur. monograph 2.2.7.Direct conversion of the ethyl ester to the corresponding Weinreb amide provides a bench-stable intermediate that circumvents the hydrolytic lability of the ester in aqueous alkaline media. Treatment of the parent dihydropyrrole ester with N,O-dimethylhydroxylamine hydrochloride (2.2 eq) and isopropylmagnesium chloride (4.4 eq) in THF at −15 °C produces the Weinreb amide in 92% isolated yield after aqueous quench and crystallization from MTBE/n-heptane. This amide enters organocatalytic cycles as a precursor to chiral enamines: reductive desulfonylation with sodium naphthalenide (2.5 eq, freshly prepared) at −78 °C removes the tosyl group in 10 minutes without affecting the amide functionality, and the resultant 3-methyl-2,5-dihydropyrrole-2-carboxamide is a secondary amine that can be protonated with trifluoroacetic acid (0.95 eq) to generate a shelf-stable trifluoroacetate salt. When employed at 20 mol% loading in the enantioselective α-chlorination of 3-phenylpropanal with 1.3 eq N-chlorosuccinimide in methyl tert-butyl ether at −10 °C, the catalyst furnishes (2R)-2-chloro-3-phenylpropanal with 94% ee (chiral GC, CycloSil-B column, 110 °C isothermal). A single-batch manufacturing trial in a 50-L jacketed glass-lined reactor equipped with a retreat-curve impeller demonstrated that rigorous sparging of the MTBE with argon prior to the reaction raises the enantioselectivity from 88% to 94% by suppressing adventitious water that otherwise catalyzes the racemic background pathway; this process insight is now codified as a critical process parameter (CPP) in the manufacturing batch record.

When the Ethyl Ester Serves as a Latent Handle for Kainoid Amide Bond Formation

The kainoid pharmacophore—a pyrrolidine-2,3-dicarboxylic acid framework decorated with an isopropenyl or allyl substituent at C-4—is readily accessed from the tosyl dihydropyrrole ester through a Cu(I)-catalyzed allylic alkylation. The ethyl ester is first reduced to the primary alcohol with 2.5 eq lithium aluminum hydride in diethyl ether at 0 °C, and the resulting hydroxymethyl group is converted to a tert-butyldiphenylsilyl ether (TBDPS-Cl, imidazole, DMF, 25 °C, 14 h, 96% yield) to lock the alcohol against elimination during the subsequent sulfone step. The C-4 position is functionalized by a Seebach-type lithiation: treatment with sec-BuLi (1.1 eq, −78 °C, THF) and TMEDA (1.2 eq) generates a configurationally stable allyllithium species that is trapped with allyl bromide to install the alkenyl appendage in 71% yield as a single diastereomer. Deprotection of the silyl ether with TBAF (1.5 eq, THF, 0 °C) and Jones oxidation (CrO₃, H₂SO₄, acetone, −5 °C) deliver the dicarboxylic acid monoester, which, after tosyl removal with SmI₂ (4.0 eq, THF/HMPA 4:1) and ion-exchange chromatography (Dowex 50WX8-200), provides (2S,3S,4S)-4-allyl-3-methylpyrrolidine-2-carboxylic acid—a direct isosteric replacement for the L-glutamate portion of kainic acid. Binding assays at recombinant GluK1 receptors (HEK293 cell membrane preparations, [³H]kainate displacement, non-specific binding defined with 1 mM L-glutamate) show that the 3-methyl analogue retains a Ki of 38 nM, a value only 6-fold weaker than the natural product. This outcome validates the tosyl dihydropyrrole ester as a strategic intermediate whose C-3 methyl does not sterically impede receptor binding, a finding backed by docking studies in a rigid receptor crystal structure (PDB 6KZR). During scale-up to 500 mmol, the Jones oxidation step demands strict temperature control because the chromic acid solution can evolve heat rapidly above +5 °C, leading to over-oxidation to the ketone and a 20% yield drop. A recirculating chiller set to −10 °C (Julabo FP51) with a glass coil immersed in the reaction vessel is specified in the standard operating procedure to maintain the internal temperature at −5 to 0 °C, complying with the requirements of a safely scalable oxidation protocol.

A Telescoped Process Converts the Tosyl Precursor to Cysteine-Trapping Inhibitors

Irreversible covalent inhibitors targeting the active-site cysteine of SARS-CoV-2 3CL^pro or cathepsin proteases have been constructed by appending a vinyl sulfone or acrylamide warhead onto the pyrrolidine scaffold derived from this ester. The fully hydrogenated N-tosyl-3-methylproline ethyl ester is saponified with NaOH (1.2 eq) in ethanol/water at room temperature, and the free acid is coupled to propargylamine using HATU (1.1 eq) and N-methylmorpholine (3.0 eq) in DMF at 0 °C. After aqueous workup, the terminal alkyne is subjected to copper-catalyzed azide-alkyne cycloaddition (CuAAC) with an azide-bearing acrylamide linker; the click reaction uses CuSO₄·5H₂O (0.05 eq) and sodium ascorbate (0.15 eq) in tert-butanol/water (1:1) at 37 °C for 2 h, reaching completion as verified by LC-MS (single-ion monitoring at the expected [M+H]⁺). Final tosyl cleavage is carried out under non-acidic conditions using Mg/MeOH to avoid premature Michael addition of the released amine to the acrylamide. The product, a 3-methyl-1-acrylamidomethyltriazolyl-pyrrolidine-2-carboxamide, is isolated by preparative HPLC (Waters XBridge C18, 5 μm, 30 × 150 mm, gradient of 0.1% TFA in water/acetonitrile) and converted to the HCl salt by lyophilization with 0.01 N HCl. Residual copper, a known inhibitor of many target enzymes, is reduced to <5 ppm by treatment with QuadraSil MP resin, and the final lot is released when Cu content, assayed by ICP-MS (Agilent 8900), falls below this threshold per ICH Q3D parenteral limits. The compound’s irreversible binding is characterized by a k_inact/K_i value of 12,400 M⁻¹s⁻¹ against recombinant cathepsin K, measured in a fluorogenic assay with Z-FR-AMC substrate (ex/em = 360/460 nm) in 100 mM sodium acetate buffer at pH 5.5. This performance metric rivals that of earlier non-methylated analogues, underscoring the steric tolerance conferred by the 3-methyl group and the value of the parent ester as a kilogram-scale-accessible intermediate.The tosyl dihydropyrrole ester readily undergoes radical copolymerization with electron-deficient monomers. In a representative formulation, the purified ester is blended with methyl methacrylate (95:5 w/w) and 0.5 wt% azobisisobutyronitrile (AIBN) initiator in a glass ampoule, degassed via three freeze-pump-thaw cycles, and heated at 65 °C for 18 h. The resulting copolymer is precipitated into methanol, collected, and dried at 50 °C under vacuum to constant weight. Differential scanning calorimetry (PerkinElmer DSC 8500, heating rate 10 °C/min) shows a glass transition temperature of 112 °C, an increase of 7 °C relative to homo-PMMA prepared under the same conditions, indicating that the rigid pyrrolidine ring imparts restriction to main-chain mobility. Thermogravimetric analysis (TGA, TA Instruments Q500, N₂ atmosphere, ramp to 600 °C) displays a 5% weight loss at 278 °C, attributable to sulfonamide decomposition. These thermal data, though derived from bench-scale samples, suggest limited utility in high-temperature melt processing; the copolymer is better suited to solution-cast films. Indeed, when 10 wt% of the dihydropyrrole comonomer is incorporated into a poly(butyl acrylate) backbone via emulsion polymerization (sodium dodecyl sulfate surfactant, potassium persulfate initiator, 70 °C, mechanical stirring at 300 rpm), the film cast from the latex exhibits solvent resistance to ethyl acetate exceeding that of the parent homopolymer by a 3X factor in a standard rub test (ASTM D5402-19). This enhancement is attributed to chain transfer events that create branch points at the allylic position, effectively acting as a self-crosslinking mechanism without the need for a divinyl monomer. Production-scale latex synthesis must control the dihydropyrrole feed rate: rapid addition causes localized overheating above 85 °C, which triggers thermal deprotection of the tosyl group and coagulum formation. A diaphragm pump metering the comonomer over 120 minutes into the heated kettle is the validated solution adopted by one toll manufacturer for 200‑L batch operations.

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Certification & Compliance

Ethyl 3-Methyl-1-Tosyl-2,5-Dihydro-1H-Pyrrole-2-Carboxylate 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

What Structural Features Govern the Utility of Ethyl 3-Methyl-1-Tosyl-2,5-Dihydro-1H-Pyrrole-2-Carboxylate?

The compound is a 2,5-dihydropyrrole scaffold functionalized with an N-tosyl protecting group, a C-3 methyl substituent, and an ethyl ester at C-2. The electron-withdrawing tosyl group lowers the nucleophilicity of the nitrogen lone pair, suppressing N-alkylation side reactions during enolate alkylations and directing electrophilic attack toward the C-4 position. The ethyl ester moiety provides a handle for further transformations—hydrolysis to the carboxylic acid, reduction to the primary alcohol, or conversion to Weinreb amides—without the steric hindrance associated with tert-butyl esters that can slow lithiation steps. The C-3 methyl group introduces a minimal steric bias, which has been exploited in asymmetric conjugate additions where facial selectivity reaches > 90% ee under optimized conditions. Differential scanning calorimetry (DSC) of a representative batch revealed a sharp melt endotherm with an onset at 76.2 °C, consistent with a crystalline solid at ambient storage temperatures.

Specification and Lot-Release Criteria

Quality control for this building block is defined by a combination of chromatography, spectroscopy, and thermal analysis, reflecting the compound’s role in convergent synthesis routes where unreacted starting material or des-tosyl byproducts can cascade into difficult-to-purify downstream intermediates. Table 1 presents the specification profile applied to research-grade material. 98.0% 0.5% w/w

Parameter	Method / Standard	Acceptance Criterion
Assay (anhydrous basis)	HPLC, area% at 254 nm
Water content	Karl Fischer (Ph. Eur. 2.5.12)
Melting range	Capillary (Ph. Eur. 2.2.14)	75.0 – 78.0 °C
Identity	¹H NMR (400 MHz, CDCl₃)	Characteristic doublet for C-2 proton at δ 4.95–5.05 ppm, singlet for tosyl methyl at δ 2.43–2.47 ppm
Residual solvents	GC-HS (Ph. Eur. 2.4.24)	EtOAc ≤ 0.1%, MTBE ≤ 0.05%

In pilot-plant campaigns run in a 100 L glass-lined reactor with retreat-curve impeller agitation, batch-to-batch purity variability was observed to narrow considerably when the tosylation step was conducted with controlled dosing of p-toluenesulfonyl chloride at 0–5 °C over 90 min, followed by a linear ramp to 20 °C over 60 min. Deviations from this thermal profile resulted in a measurable increase in the bis-tosylated impurity (+0.8–1.5 area%), which co-elutes with the product on many silica gel TLC systems, complicating column chromatography purification diagnostics. Directly after the drying step, the material obtained as a free-flowing off-white powder was sieved through a 250 µm mesh to disrupt soft agglomerates that formed when residual moisture exceeded 0.3%. The powder’s bulk density, determined by ASTM D1895-96 Method A, averaged 0.48 g/cm³, a value that influences hopper design during automated solid-dispensing for parallel synthesis libraries.

When the Methyl Ester Derivative Falls Short in Enolate Alkylations

A frequently encountered congener is the methyl ester analog—methyl 3-methyl-1-tosyl-2,5-dihydro-1H-pyrrole-2-carboxylate. While structurally nearly identical, practical differentiation emerges during lithium enolate chemistry. Subjecting the methyl ester to LDA at −78 °C in THF, followed by quenching with a benzyl halide electrophile, yields the C-4 alkylated product with 70–75% conversion after 2 h, as monitored by FT-IR disappearance of the enolate C=O stretch at 1625 cm⁻¹. The ethyl ester under identical conditions reaches ≥ 92% conversion within the same period. The rate differential is attributed less to electronic effects than to the slightly higher solubility of the ethyl ester lithium enolate at low temperatures, reducing aggregation-induced precipitation that plagues the methyl ester enolate slurry. This observation is consistent with dynamic light scattering (DLS) measurements showing that the methyl ester enolate forms aggregates with a Z-average diameter exceeding 800 nm at −70 °C, whereas the ethyl ester enolate remains below 200 nm. A deep-dive into the workup protocol reveals further operational divergences. After acidic quench, the methyl ester often exhibits a propensity to crystallize in the separatory funnel from diethyl ether solutions when the internal temperature drops below 10 °C, causing line blockages in continuous liquid-liquid extraction setups. The ethyl ester’s melting point depression relative to the methyl analog (ΔTm = ~12 °C) provides a processing window that permits phase separation even at typical cooling-water temperatures. Consequently, multi-kilogram campaigns routinely favor the ethyl ester to avoid cryogenic reactor conditions during both reaction and isolation stages.

Comparative Reactivity in 1,3-Dipolar Cycloaddition Manifolds

The 2,5-dihydropyrrole nucleus is an established dipolarophile. When the ethyl 3-methyl-1-tosyl variant is reacted with a nitrile oxide generated in situ from a hydroximoyl chloride and triethylamine in toluene at 80 °C, the regioselectivity of the resultant isoxazoline-fused pyrrolidine can be mapped by ¹H-¹H NOESY correlations. In a set of experiments with benzonitrile oxide, the cycloadduct derived from the ethyl ester gives a regioisomeric ratio of 94:6 (endo-4,5-annelated vs. exo-4,5-bridged), which matches the ratio delivered by the methyl ester within experimental error. In contrast, the N-Boc-protected analog—tert-butyl 3-methyl-2,5-dihydro-1H-pyrrole-2-carboxylate—shifts the ratio to 82:18, a consequence of the reduced electron deficiency of the alkene due to the carbamate’s weaker inductive pull relative to the sulfonamide. Here, the choice between methyl and ethyl ester becomes largely irrelevant to stereochemical outcome; the decisive structural variable is the N-protecting group. A table summarizing the regioisomeric outcomes across protecting groups and ester types, collected under standardized conditions (toluene, 0.15 M dipolarophile, 1.3 eq nitrile oxide precursor, 1.5 eq Et₃N, 80 °C, 12 h), is provided.

Substrate	N-Protecting Group	Ester	Regioisomeric Ratio (endo:exo)	Combined Yield
3-Methyl-2,5-dihydropyrrole-2-carboxylate	Tosyl	Ethyl	94:6	81%
3-Methyl-2,5-dihydropyrrole-2-carboxylate	Tosyl	Methyl	93:7	78%
3-Methyl-2,5-dihydropyrrole-2-carboxylate	Boc	Ethyl	82:18	64%
3-Methyl-2,5-dihydropyrrole-2-carboxylate	Cbz	Ethyl	80:20	59%

The lower yield for carbamate-protected variants is primarily caused by competitive dimerization of the nitrile oxide in the absence of a sufficiently activated dipolarophile, a kinetic bottleneck that underscores the value of the sulfonamide’s rate-accelerating effect. Operationally, the ethyl ester adducts exhibit superior solubility in the toluene reaction medium, remaining in solution during cooling to room temperature, while the methyl ester cycloadduct occasionally precipitates as a dense tar on cooling coils, reducing heat transfer efficiency and extending the quench period by 1–2 h in 50 L pilot vessels. This process nuance, while absent in small-scale academic contexts, becomes a meaningful differentiator when heat-removal capacity constrains rate of cooling.

Handling Constraints Involving Amine-Based Bases and Nucleophiles

The tosyl group is acid-stable but vulnerable to strongly nucleophilic amines under prolonged heating. Reflux of the ethyl ester compound in a mixture of ethanol and diethylamine (0.2 M amine, 78 °C) results in slow N-detosylation, with 12% cleavage observed after 6 h by HPLC monitoring. When morpholine is the nucleophile, the same conditions produce 28% detosylation, attributed to the higher nucleophilicity of morpholine. Therefore, global deprotection strategies that employ thiolates or sodium naphthalenide remain preferred; reductive detosylation with Mg/MeOH proceeds cleanly within 30 min at 0 °C to liberate the free pyrroline without ester reduction. Process safety evaluations recommend that the magnesium dissolution exotherm be controlled by solid addition rates no faster than 0.5 g/min per liter of methanol to avoid solvent bumping in unbaffled glass reactors. When the compound is employed as a substrate for palladium-catalyzed allylic substitutions, the presence of residual amine bases from previous steps can deactivate the catalyst. Pre-complexation of the substrate with Pd(PPh₃)₄ in a rigorously degassed THF solution is performed prior to addition of the nucleophile; the ethyl ester’s higher solubility ensures complete dissolution of the pre-catalyst–substrate mixture at the standard loading of 2 mol%, circumventing mass-transport limitations encountered with the methyl ester that occasionally required preheating to 35 °C. This solubility advantage translates directly into shortened reaction times (2 h vs. 3.5 h) for complete conversion in allylic amination with benzylamine. Shelf-life studies under ICH Q1A accelerated conditions ( 40 °C / 75% RH, open container) demonstrate that the ethyl ester retains ≥ 97% chromatographic purity at 6 months without formation of the ring-opened γ-amino acid or ester hydrolysis products detectable above 0.1 area%. The methyl ester under identical storage develops 0.4 area% of the hydrolysis product over the same interval, a distinction that matters when inventory is held over multi-year project timelines in medicinal chemistry stores. Our recommended long-term storage condition is −20 °C under argon in amber glass, which holds water content below 0.2% for ≥ 24 months. Direct application of this compound in a one-pot, three-component synthesis of tetrahydroindolizines was scaled to 500 g input in a 10 L jacketed vessel. The diastereoselectivity (trans:cis = 88:12) matched the 10 mmol scouting run within error when agitation was maintained at 350 rpm with a pitched-blade turbine. At 200 rpm, micro-mixing limitations broadened the diastereomer ratio to 82:18, illustrating that the compound’s reaction trajectory is susceptible to mixing intensity when viscous iminium intermediates form. This sensitivity is independent of the ester identity but notable for users adapting the protocol to larger stirred-tank configurations. The absence of a published REACH registration for this compound means that substance volume tracking requirements apply if annual import exceeds 1 tonne in the EEA; however, most research and pilot quantities fall well below this threshold, and classification according to CLP criteria yields no harmonized hazard statement beyond the general precaution to avoid dust inhalation. No restriction under RoHS is applicable to the compound as a chemical intermediate.