1-Amino-1H-Pyrrole-2-Carboxamide

Within the progression from preclinical candidate selection to the synthesis of a pyrrolo[1,2-a]pyrazin-2-one pharmacophore intended as a non-structural protein 5B (NS5B) inhibitor, 1-amino-1H-pyrrole-2-carboxamide functions as the irreplaceable primary amine donor that furnishes the planar pyrrole ring and the dual hydrogen-bonding motif required for enzymatic pocket recognition. Coupling to an elaborated carboxylic acid fragment employs a standard carbodiimide protocol in anhydrous dichloromethane–dimethylformamide 4:1 v/v, with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride at 1.25 eq and 1-hydroxybenzotriazole hydrate at 1.30 eq, keeping the amino heterocycle at exactly 1.00 eq to avoid the formation of a bis-acylated impurity that co-elutes with the product during normal-phase chromatography. The addition of the acid–activating cocktail is conducted under positive nitrogen atmosphere with the jacket temperature set to −2 °C; in-line FTIR monitoring (Mettler Toledo ReactIR 15) tracks the disappearance of the acid carbonyl stretch at 1750 cm⁻¹ and the appearance of the amide II band at 1540 cm⁻¹. A reaction temperature excursion above +8 °C triggers an autocatalytic N→O acyl migration pathway that elevates the structurally related regioisomer from 0.3% to 2.5% peak area by HPLC in less than 45 minutes, necessitating an automated shut-off interlock tied to the jacket temperature probe. After aqueous work-up and phase separation in a vertical disc-stack centrifuge, the crude intermediate is purified on a simulated moving bed (SMB) chromatographic unit (Kromasil C₁₈ 10 µm, ethanol–water with 0.1% formic acid) to achieve a chemical purity of ≥99.5% and an individual unspecified impurity ceiling of ≤0.10%, in alignment with ICH Q3A and Q3B requirements for new drug substances. A critical alert pertains to the potential generation of a mesityl oxide-aldol condensation adduct if the batch contains residual acetone from equipment cleaning; therefore the SMB feed solution is tested for acetone by headspace GC–FID with a reporting threshold of 50 ppm (USP <467>). The isolated intermediate is dried in a conical tumble dryer at 35 °C/10 mbar for 18 hours, yielding a white crystalline powder with a water content below 0.15% (Karl Fischer titration, USP <921>) and a residual solvent profile compliant with ICH Q3C Option 2. Downstream, the compound undergoes palladium-catalysed direct C–H activation and intramolecular cyclisation in a continuous flow microreactor (Corning Advanced-Flow reactor G1, residence time 8.5 minutes at 120 °C) to close the tricyclic core of the antiviral API, which is ultimately formulated as a film-coated tablet under FDA 21 CFR Part 211 finished pharmaceutical regulations and subjected to a genotoxic impurity purge study using the Teasdale in silico purge factor model, with confirmatory LC–MS/MS analysis targeting a nitrosamine N-nitroso-1-amino-1H-pyrrole-2-carboxamide down to a limit of quantification of 0.03 ppm in the final drug product.

How Does a Buffered Biphasic Acylation Window Stabilise the Aminopyrrole Scaffold During Synthesis of Insecticidal 2-Arylaminopyrrole-2-carboxamides?

The conversion of 1-amino-1H-pyrrole-2-carboxamide into a library of 2-aryl-substituted derivatives designed for lepidopteran ryanodine receptor modulation relies on a Schotten–Baumann acylation conducted in a water–toluene biphase. A 1.0 M sodium bicarbonate buffer maintains the aqueous phase pH between 8.2 and 8.5 during dropwise addition of a substituted benzoyl chloride (1.08 eq, dissolved in toluene 3 volumes) to a solution of the aminopyrrole in water 5 volumes at 32 °C. The 1.08 eq stoichiometry compensates for the 7–10%hydrolytic loss of the acid chloride, but exceeding 1.15 eq causes a persistent emulsion that traps unreacted aminopyrrole and reduces isolated yield by 12–15%. The Rushton turbine impeller is operated at a tip speed of 2.8 m·s⁻¹, delivering a dispersed phase Sauter mean diameter below 300 µm and ensuring the interfacial mass transfer coefficient remains above 0.012 s⁻¹ as monitored by a focused beam reflectance measurement (FBRM) probe. After phase cut, the organic layer is concentrated and the crude acylated intermediate is crystallised from methanol–water 3:1 to yield a technical-grade solid with a purity of ≥96% by HPLC area percent. The primary toxicological concern arises from the residual 1-amino-1H-pyrrole-2-carboxamide itself, which may display >0.15% dermal absorption potential as estimated by the Potts–Guy quantitative structure–permeability relationship; accordingly, a limit of 0.5% w/w in the technical concentrate is enforced, and the washing steps are repeated until the supernatant shows no UV-active spot at Rf 0.42 on silica gel 60 F₂₅₄ TLC (dichloromethane–methanol 9:1). The resulting 2-arylaminopyrrole-2-carboxamide is formulated as a 100 g·L⁻¹ suspension concentrate (SC) using an ethylene oxide–propylene oxide block copolymer dispersant at 4% w/w and milled in a horizontal bead mill with yttria-stabilized zirconia beads (0.3–0.4 mm) to a D₉₀ of 2.5 µm; the SC is stability-tested for 14 days at 54 °C per CIPAC MT 46.3. Registration data packages for the final insecticide must contain an aquatic ecotoxicology profile compliant with Regulation (EC) No 1107/2009, including an acute Daphnia magna immobilization test (OECD 202) and an algal growth inhibition test (OECD 201), with both endpoints reported as EC₅₀ values alongside the 95% confidence intervals.

1-Amino-1H-pyrrole-2-carboxamide undergoes diazotization at 0–5 °C with 1.0 eq sodium nitrite in 2.5 N hydrochloric acid and subsequent coupling to N,N-diethylaniline at pH 4.0–4.5, furnishing a yellow disperse dye suitable for polyester; the dyed fabric is evaluated for wash fastness according to ISO 105-C06:2010 and for light fastness under ISO 105-B02:2014 xenon arc exposure.

When Co-sublimed with a Non-Fullerene Acceptor, What Dopant Content Shifts the Frontier Orbital Alignment Sufficiently in Binary Organic Photovoltaic Blends?

The incorporation of 1-amino-1H-pyrrole-2-carboxamide as a solid-state p-type dopant into the bulk heterojunction of an inverted organic photovoltaic cell demands sublimation-grade material with a metal impurity burden below 10 ppm per element and a total organic volatile impurity content below 0.02%, as determined by inductively coupled plasma mass spectrometry (ICP-MS, per ASTM E2927-16e1) and thermogravimetric analysis coupled with gas chromatography (GC–TGA). The dopant is co-evaporated with a PM6:Y6 blend in a custom-built multi-source high-vacuum thermal evaporator (base pressure < 5 × 10⁻⁷ mbar) equipped with quartz crystal microbalances for each boat. The deposition rate for the dopant is held at 0.02–0.04 Å·s⁻¹, while the donor–acceptor mixture is deposited at a combined rate of 1.8 Å·s⁻¹, resulting in a dopant volume fraction of 0.8 mol% to 2.5 mol%. At 1.2 mol%, ultraviolet photoelectron spectroscopy reveals a work function increase of the blend surface from 4.3 eV to 4.65 eV, and the hole-only device dark current measured by the space-charge-limited current method yields a hole mobility enhancement from 1.4 × 10⁻⁴ cm²·V⁻¹·s⁻¹ to 3.8 × 10⁻⁴ cm²·V⁻¹·s⁻¹. However, when the dopant concentration exceeds 2.0 mol%, the fill factor collapses from 68% to below 52% due to the formation of crystallite domains visualised as dark spots in atomic force microscopy phase images; the threshold for this morphology breakdown is confirmed by grazing-incidence wide-angle X-ray scattering with a correlation peak at q ≈ 0.35 Å⁻¹ disappearing above 2.0 mol%. Device stacks are encapsulated with a UV-curable epoxy getter and a barrier film having a water vapour transmission rate below 10⁻³ g·m⁻²·day⁻¹ (MOCON test, ASTM F1249) and subjected to maximum power point tracking under continuous 1-sun AM 1.5G illumination for 1000 hours; the retained power conversion efficiency of 14.1% degrades by less than 5% relative only when the dopant is kept below the 2.0 mol% critical point. All materials used in the active layer must be free of substances restricted by the EU RoHS Directive 2011/65/EU Annex II, and the solar cell prototype is tested for compliance with IEC 61215-1:2021 regarding damp heat stability at 85 °C/85% RH for 500 hours.

The addition of 0.5 g of 1-amino-1H-pyrrole-2-carboxamide to a 100 mL aqueous sample buffered to pH 5.5 with acetate (0.05 M) allows the spectrophotometric determination of cupric ion at 420 nm through a 1:2 metal–ligand complex; the method follows the general colorimetric framework of ISO 8288:1986 and exhibits a detection limit of 0.03 mg·L⁻¹ when a 5 cm cell path length is employed.

Latent Catalytic Activity in Anhydride-Cured Epoxy Networks at Temperatures Approaching Glass Transition

1-Amino-1H-pyrrole-2-carboxamide functions as a thermally latent accelerator in methylhexahydrophthalic anhydride-cured bisphenol A diglycidyl ether systems intended for carbon fibre-reinforced composite tooling capable of service at 180 °C. The compound is dry-blended with the epoxy resin at a loading of 0.8 phr (parts per hundred resin) using a planetary centrifugal mixer at 2000 rpm for 90 s under vacuum, avoiding the need for solvent pre-dissolution that would otherwise create void-prone regions during the vacuum-assisted resin transfer moulding (VARTM) infusion. Differential scanning calorimetry at a ramp rate of 10 K·min⁻¹ reveals that the onset of curing exotherm shifts from 148 °C (unaccelerated) to 122 °C, while the peak exotherm remains sufficiently narrow to enable a staged cure cycle of 1 hour at 90 °C plus 2 hours at 160 °C plus a 4-hour post-cure at 200 °C. Rheological monitoring on an ARES-G2 rheometer using 25 mm parallel plates with a 1 mm gap shows that the complex viscosity at 100 °C stays below 0.3 Pa·s for at least 120 minutes, granting a sufficient open time for the infusion of large-area preform stacks; this contrasts with imidazole accelerators, which typically begin to build viscosity within 30 minutes at the same temperature. The latent nature originates from the protonation equilibrium of the 1-amino group by the acidic anhydride, which suppresses nucleophilic attack until steric de-shielding occurs above 110 °C. Flexural specimens machined from a quasi-isotropic [0/90/±45]_s layup and tested per ASTM D7264/D7264M-21 at 23 °C exhibit a flexural modulus of 42 GPa and strength of 620 MPa, with a glass transition temperature of 178 °C measured by dynamic mechanical analysis (three-point bending, 1 Hz, 3 K·min⁻¹). Extended oxidative ageing of the cured composite at 180 °C for 1000 hours in a forced-convection oven results in a mass loss of 1.8%, and the interlaminar shear strength (short-beam shear, ASTM D2344/D2344M-22) decreases from 48 MPa to 41 MPa, indicating acceptable thermo-oxidative stability compared to commercial phenolic-type accelerators. Fabricators who implement this accelerator in conjunction with a liquid-type silicone internal release agent should verify compatibility through a 24-hour gel time test, as certain silicone formulations chelate the pyrrole nitrogen and reduce latency by prematurely liberating the amine proton, dropping the onset temperature by as much as 15 K.