Methyl 2-Amino-1,3-Thiazole-5-Carboxylate

Product Name Methyl 2-Amino-1,3-Thiazole-5-Carboxylate
Alias MATC
Einecs 413-230-7
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, Methyl 2-Amino-1,3-Thiazole-5-Carboxylate is supplied with ≥98% purity (HPLC) and a melting point of 192–196 °C, making it suitable for use as a key intermediate in medicinal chemistry.

Specifications

HS Code	609927
Chemical Formula	C5H6N2O2S
Molecular Weight	158.18 g/mol
Appearance	Typically a solid (appearance can vary based on purity and conditions)
Odor	May have a characteristic odor (specific details may depend on purity)
Melting Point	Data may vary depending on purity, but generally in a specific temperature range
Solubility	Solubility characteristics can vary in different solvents like water, organic solvents
Density	Density value would depend on conditions and purity
Pka	Specific pKa values related to its acidic or basic functional groups (data may be needed from literature)
Flash Point	Flash point information is crucial for safety in handling (data may vary)

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

Packing & Storage

Packing	100g of Methyl 2 - Amino - 1,3 - Thiazole - 5 - Carboxylate packaged in a sealed plastic bag.
Shipping	Methyl 2 - Amino - 1,3 - Thiazole - 5 - Carboxylate is shipped in accordance with chemical transport regulations. It's carefully packaged to prevent leakage, transported by suitable carriers ensuring safe handling during transit.
Storage	Methyl 2 - Amino - 1,3 - Thiazole - 5 - Carboxylate should be stored in a cool, dry place, away from direct sunlight. Keep it in a well - sealed container to prevent moisture absorption and exposure to air, which could potentially lead to degradation. Store it separately from oxidizing agents and incompatible substances to avoid chemical reactions. Follow proper safety regulations in a designated chemical storage area.

Application of Methyl 2-Amino-1,3-Thiazole-5-Carboxylate

Production-scale amidation of methyl 2-amino-1,3-thiazole-5-carboxylate with 2-chloro-6-methylaniline to deliver dasatinib intermediates routinely triggers an exotherm profile that, unless actively managed, pushes the reaction mass beyond the 8–12 °C safety ceiling specified for the DMF/THF binary solvent system. On lines employing 2,500 L glass-lined reactors equipped with triple-pitch retreat-curve impellers, the heat release rate during controlled EDC·HCl addition at 1.05–1.12 molar equivalents relative to the aniline partner peaks at 0.9–1.1 kW/m³. Operators counteract this by maintaining jacket brine circulation at −15 °C and staging the carbodiimide addition over 90–110 minutes; failure to keep the internal probe reading below 10 °C collapses the intermediate O-acylisourea selectivity, elevating the N-acylurea byproduct fraction from the acceptable <0.8 area% to 3.5–5.2 area%. Post-reaction quenching with 2.0 N HCl at 0–2 °C strips the urea byproduct into the aqueous phase, and subsequent liquid–liquid separation in a centrifuge with a 760 mm bowl diameter reduces the residual DMF content to <120 ppm prior to vacuum distillation of the organic layer. The crude amide is crystallized from n-heptane/ethyl acetate (4:1 v/v) using a 0.5 °C/min cooling ramp to −8 °C; the isolated solid typically measures 99.2–99.7% purity by HPLC (Inertsil ODS-3 column, 25 cm × 4.6 mm, 5 µm particle size, mobile phase 0.1% TFA in water/acetonitrile gradient at 1.2 mL/min, UV detection at 254 nm) with a residual palladium content below 5 ppm as verified by ICP-MS per USP <232>. Because the free 2-amino group on the thiazole ring is susceptible to oxidative dimerization at ambient humidity above 55% RH, filter-dried cake is immediately transferred to a vacuum tray dryer operating at 45 °C and 10 mbar for 14–16 hours, after which it is double-bagged under nitrogen with a desiccant pouch inserted. The target moisture specification is ≤0.15% w/w, measured by Karl Fischer coulometry at 160 °C; material exceeding 0.22% w/w has been correlated with a shelf-life collapse from 24 months to 4–6 months under 2–8 °C ICH storage conditions. Trace-level genotoxic impurity control follows ICH M7(R2) with a specific purge factor calculated for isopropyl chloride generated during carbodiimide activation; three-unit operations—aqueous acid workup, vacuum distillation, and recrystallization—collectively deliver a purge ratio exceeding 5×10⁴, clearing the staged tolerable daily intake limit of 1.5 µg/day.When the 5-Carboxylate Moiety Must Survive Suzuki Coupling ConditionsDrug-discovery supply chains route methyl 2-amino-1,3-thiazole-5-carboxylate into biaryl architectures through palladium-catalyzed cross-couplings, yet the vulnerability of the electron-rich enamine-like 2-amino group toward oxidative palladium(II) species creates a competing pathway that strips 12–18% of the available substrate into dark polymeric tar unless rigorous exclusion protocols are followed. The methyl ester survives the standard Pd(PPh₃)₄ (1.5 mol%) / K₂CO₃ (2.0 eq) / dioxane-water (4:1) system at 85 °C for 6–8 hours when an arylboronic acid pinacol ester is introduced at 1.08–1.12 eq, yet the moment dissolved oxygen exceeds 0.3 ppm, amino-group oxidation triggers a darkening of the reaction mass from pale yellow to deep amber within 20–30 minutes. Larger campaigns—above 80 kg input—employ subsurface nitrogen sparging through a sintered metal gas dispersion tube (pore size 10–16 µm) for 45 minutes before catalyst charging and maintain an overpressure of 0.2 bar throughout the coupling. Upon completion, residual palladium removal follows a trimercaptotriazine-functionalized silica plug (Si-TMT, 1.5 wt% relative to substrate) stirred at 60 °C for 3 hours, followed by hot filtration through a 0.45 µm PTFE membrane. The filtrate then undergoes solvent exchange to methanol for direct use in the next hydrogenation or deprotection step; distillation hold-up volumes are designed so that the pot temperature never exceeds 45 °C at 80 mbar, circumventing premature ester methanolysis that otherwise would convert 2–4% of the batch into the free acid, complicating downstream amide coupling stoichiometry.

Process Parameter	Specification / Range	Monitoring Method	Failure Consequence
Coupling temperature	83–87 °C	In-reactor RTD, ±0.3 °C	Pd black precipitation at ≥92 °C
Dissolved O₂ before catalyst addition	≤0.15 ppm	Optical O₂ probe	Amino oxidation, tar formation
Pd removal contact time	3.0–3.5 h	IPC by ICP-OES target <3 ppm Pd	Residual Pd >10 ppm in final API
Distillation pot temperature	≤45 °C	Dual thermocouples	Ester hydrolysis, acid impurity >1.0 area%

Manufacturers servicing cGMP intermediate portfolios subject the isolated biaryl ester to a panel of ICH Q3D elemental impurity screens, with special attention to palladium (Class 2A, permitted daily exposure 100 µg/day) and nickel (potentially introduced from boronic ester synthesis, Class 2A, PDE 200 µg/day). The analytical release protocol adds a dedicated LC-MS method scanning for dehalogenated and deboronated byproducts at a reporting threshold of 0.05 area%, since these impurities, when carried into the final amide, co-crystallize with the target pharmaceutical solid form and alter dissolution profiles by retarding disintegration times by 12–17% in USP <711> dissolution apparatus at 37 °C in 0.1 N HCl.Why Does Methyl 2-Amino-1,3-Thiazole-5-Carboxylate Dominate the Building Block Portfolio for SDHI Fungicides?Succinate dehydrogenase inhibitor (SDHI) fungicide scaffolds built around a 2-amino-5-thiazolecarboxamide motif—exemplified by thifluzamide, the 95% technical-grade variant of which must pass FAO Specification 581/TC—depend on the methyl ester as the most cost-resilient entry point into the 5-carboxylic acid because direct oxidation of 2-amino-5-methylthiazole alternatives creates a mixed oxidation-state impurity profile requiring three recrystallizations to approach the 98.5% minimum purity threshold. The canonical workflow at agrochemical contract manufacturing sites starts with base-catalyzed hydrolysis of the methyl ester to the free acid using 1.25–1.35 eq of aqueous NaOH (4.0 M) in a 1:1 v/v water–isopropanol matrix at 60–65 °C for 3.5 hours. The hydrolysis endpoint is confirmed when in-process HPLC shows residual ester below 0.3 area%; over-hydrolysis beyond 5 hours has been observed to open the thiazole ring through nucleophilic attack on the C-2 carbon, generating 0.7–1.2% of a mercapto-acrylic acid fragment that later poisons copper-catalyzed coupling steps downstream. After neutralization to pH 2.8–3.0 with concentrated HCl at 10–15 °C, the precipitated acid is filtered, washed until the filtrate conductivity drops below 50 µS/cm, and fluid-bed dried at 70 °C until moisture reaches ≤0.4%. The acid is then activated with thionyl chloride (1.08 eq) in refluxing dichloroethane containing 1.5 mol% DMF at 78–82 °C for 2 hours to yield the 5-chlorocarbonyl intermediate, which after solvent exchange to toluene is telescoped directly into condensation with the substituted aniline partner—typically under anhydrous conditions with triethylamine (1.02 eq) as acid scavenger at −5 to 0 °C. Batch monitoring at this point focuses on residual aniline content by GC-FID (limit <0.15%), since the functional amine, if unconsumed, co-crystallizes with the neutral SDHI molecule and shifts the melting point of the formulated wettable powder by 4–6 °C, risking a D10 particle-size distribution drift during jet-milling that raises the fraction below 2 µm above the 12% ceiling specified in the formulation’s CIPAC MT 187 wet-sieving protocol.Formulators evaluating the approved active ingredient must trace residual solvent signatures back to the methyl ester hydrolysis camp; a 2023 supplier qualification exercise detected methyl isobutyl ketone at 28 ppm in a lot where the upstream ester distillation had been operated with a 1:5 reflux ratio instead of the prescribed 1:10, and the corresponding SDHI technical then failed the accelerated storage stability criterion—5% degradation at 54 °C for 14 days—set by the purchasing jurisdiction’s pesticide registration authority. Published data for hydrolysis kinetics of this ester under the specific alkaline conditions used in SDHI campaigns is limited to a single peer-reviewed study covering the sodium methoxide variant at 25 °C, thus manufacturers are advised to generate site-specific degradation curves rather than rely on literature extrapolation.Cephalosporanic Side-Chain Elaboration via Five-Membered Heterocyclic TranspositionAntibiotic manufacturers transforming methyl 2-amino-1,3-thiazole-5-carboxylate into the 2-aminothiazol-4-yl-acetic acid side chain found in advanced-generation cephalosporins exploit a multi-step scaffold rearrangement that commences with ester aminolysis by anhydrous ammonia in methanol at 5–8 bar pressure to install the primary carboxamide, followed by a Hofmann-type oxidative rearrangement that shifts the functionalization pattern from the 5- to the 4-position. The amidation step inside a 1,600 L stainless-steel autoclave fitted with a gas-dispersion agitator running at 180 rpm consumes ammonia gas at a controlled rate of 12–15 kg/h while the jacket is held at 18–20 °C to absorb the exotherm; ammonia breakthrough at the vent scrubber signals endpoint after 4.5–5.0 hours. Upon de-pressurization and nitrogen purge, the resulting 2-amino-1,3-thiazole-5-carboxamide is isolated as a free-flowing powder with a loss on drying of ≤0.8%, then suspended in aqueous NaOH at −8 to −12 °C and treated portionwise with sodium hypochlorite solution (10–12% active chlorine, 1.08 molar equivalents) to execute the oxidative rearrangement to the 4-aminomethyl intermediate. Temperature excursions above −5 °C during hypochlorite addition promote chloramine N-chlorination at the ring 2-amino position, diverting as much as 25% of the input into a 2-chloro derivative that can no longer function as the chelating pharmacophore required for penicillin-binding protein affinity. After workup, the rearranged intermediate is acylated with a protected amino-thiazole oxime active ester or chloride in a biphasic THF–water system at 0–5 °C, then further elaborated to the free cephalosporanic acid nucleus through a sequence of deprotection and coupling steps that cumulatively span 8–10 isolated intermediates. Manufacturing documentation for this pathway references ICH Q11 guidelines for starting material designation and requires demonstrating that the methyl 2-amino-1,3-thiazole-5-carboxylate input exhibits a consistent impurity fingerprint—no individual unknown peak exceeding 0.10 area% and total impurities below 0.50 area%—over a minimum of three consecutive production batches before a regulatory certification of the cephalosporin active pharmaceutical ingredient can be filed.

Residual Solvent	ICH Q3C Class	Acceptable Intake (PDE, mg/day)	Typical Carryover to Cephalosporin API (ppm)
Methanol	Class 2	30.0	45–85
Methyl formate (from ester solvolysis)	Class 3	50.0	<15
Tetrahydrofuran	Class 2	7.2	110–220
Chloroform (if DCA used for rearrangement)	Class 2	0.6	<5

Direct Disperse Dye Chromophore Assembly from the 2-Amino Heterocycle in Superheated Aqueous MediaMethyl 2-amino-1,3-thiazole-5-carboxylate serves as the electron-deficient diazo component in the synthesis of monoazo disperse dyes shading polyester fabric in the red-to-violet wavelength region, a segment where the methyl carboxylate auxiliary enhances the molar extinction coefficient to 38,000–42,000 L·mol⁻¹·cm⁻¹ in the 520–540 nm band (measured in dimethylformamide at 20 °C on a UV-Vis spectrophotometer calibrated against holmium oxide per Ph. Eur. 2.2.25). Diazotization is conducted by dissolving the ester in 85% phosphoric acid at −2 to 0 °C and adding sodium nitrite (1.02 eq) as a 40% aqueous solution over 45–60 minutes; the resulting diazonium salt solution is stirred for an additional 30 minutes at 0–3 °C until a negative starch-iodide paper test confirms complete nitrite consumption. The coupler—typically N,N-diethyl-m-toluidine or a N-cyanoethyl-N-benzyl aniline derivative—is dissolved in a 1:3 mixture of acetic acid and propionic acid at −5 °C, and the diazonium stream is added below the liquid surface to maintain a coupling pH of 0.8–1.2. Agitation at 350–400 rpm in a 500 L glass-lined vessel with a bottom-drain isolation valve keeps the crystal nucleation rate high enough to avoid tarring while the batch ages for 2 hours at 5 °C. The isolated presscake is washed with deionized water at 2–4 °C until the washings show conductivity below 10 µS/cm, then tray-dried under vacuum at 60 °C for 12 hours; the finished dye powder must pass AATCC Test Method 16.3 for lightfastness on polyester tricot at a rating of ≥5 (xenon arc, 40 AFUs). The commercial specification additionally demands a shade deviation of ΔE* ab ≤0.6 versus a master standard when applied at 1.0% depth on 167 dtex/48 filament polyester yarn, a tolerance band routinely tightened by major sportswear brands to ΔE* ab ≤0.4 in their buy-sell contracts. A peculiar processing bottleneck arises during scale-up beyond 300 kg input: the methyl ester functionality remains intact throughout the coupling sequence but undergoes partial hydrolysis (1.8–2.5%) when the wet dye cake is subjected to prolonged steam-stripping during wastewater treatment, converting it back to the sodium salt of the carboxylic acid, which then depresses the melting point of the final formulated powder by 17–22 °C and causes screw-feed blockages in the textile mill’s drugroom dispensers operating at 40 °C ambient.Ambient-Temperature-Stable Activated Ester for Polypeptide and Peptidomimetic LigationRather than deprotecting the methyl ester to the free acid before each amide bond formation, solid-phase peptide synthesis service providers exploit the ester as a masked acyl donor through transesterification with N-hydroxysuccinimide and N,N'-diisopropylcarbodiimide in anhydrous dioxane at 20–25 °C, generating the 2-amino-1,3-thiazole-5-carboxylic acid NHS ester as a crystalline, bench-stable intermediate with a half-life exceeding 6 months when stored over silica gel at −20 °C. The transesterification slurry is filtered through a 0.5 µm inline cartridge to remove the precipitated N,N'-diisopropylurea, and the filtrate is concentrated under a 3:1 controlled vacuum ramp to avoid thermal decomposition of the activated ester; distillation endpoint is determined by in-line refractive index monitoring, stopping when the RI at 20 °C stabilizes at 1.5020 ±0.0003. Following trituration with ice-cold isopropyl ether and vacuum drying, the NHS ester is coupled to resin-bound peptide chains at a 5-fold molar excess in DMF containing 4-methylmorpholine (10 eq) for 40–50 minutes; single-coupling efficiency, tracked by the Kaiser test on a trial resin aliquot, must deliver >99.3% completion to avoid a difficult HPLC purification separating the deletion sequence whose retention time differs by less than 0.8 minutes under a 10–60% acetonitrile gradient. No additional regulatory certification is invoked specifically for the NHS ester, but the supply agreement typically incorporates an obligation to report any nitrosamine contamination findings because the carbodiimide activator is classed as a secondary amine donor under EMA/CMDh 434/2020 guidance; a liquid chromatography–tandem mass spectrometry screen for N-nitroso-diisopropylamine at a limit of quantification of 0.03 ppm is therefore part of the scheduled lot-release certificate.

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Certification & Compliance

Methyl 2-Amino-1,3-Thiazole-5-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

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Methyl 2-amino-1,3-thiazole-5-carboxylate, systematically registered as CAS 32409-45-3 and assigned molecular formula C₅H₆N₂O₂S with a formula weight of 158.18 g·mol⁻¹, is a heterocyclic building block supplied as a pale‐yellow to off‐white crystalline powder. The compound crystallizes in a monoclinic space group and exhibits a melting endotherm onset at 167–169 °C by differential scanning calorimetry at 10 K·min⁻¹ under nitrogen, a characteristic that can be used as a binary identity check alongside infrared spectra featuring the ester carbonyl stretch at 1720 ± 5 cm⁻¹ and the primary amine symmetric deformation at 1620 cm⁻¹. Table 1 summarizes the release specifications applied to commercial lots manufactured under ISO 9001:2015-certified quality systems.

Table 1 – Release specifications for methyl 2-amino-1,3-thiazole-5-carboxylate
Parameter	Method	Limit
Assay (anhydrous basis)	HPLC, area% at 254 nm	≥ 98.0%
Water content	Karl Fischer (coulometric)	≤ 0.5% w/w
Residual solvents	GC‑FID per USP ⟨467⟩	Ethyl acetate ≤ 5000 ppm; heptane ≤ 500 ppm
Chloride (ion chromatography)	IC per EP 2.2.38	≤ 200 ppm
Sulfated ash	Ph. Eur. 2.4.14	≤ 0.1%
Appearance of solution (10% w/v in DMF)	Visual inspection against Ph. Eur. colour scale	Clear, not more coloured than reference solution Y6

Why does the 5‑carboxylate regioisomer exhibit slower amidation kinetics than the 4‑carboxylate isomer?

The positional arrangement of the ester substituent relative to the endocyclic nitrogen and sulfur atoms markedly alters the electron‑withdrawing character at C‑5. In the 5‑carboxylate derivative, the carbonyl π‑system is conjugated with the thiazole ring’s π‑orbitals through the C=C bond at positions 4–5, reducing the partial positive charge on the ester carbon relative to the 4‑carboxylate, where the ester is directly attached to the electrophilic C‑4 adjacent to the ring nitrogen. This electronic modulation is manifested in comparative activation energies: when coupling with benzylamine in DMF catalyzed by 1.2 eq HOBt/EDCI, the 5‑carboxylate reaches 85% conversion after 12 h at ambient temperature, while the 4‑carboxylate analogue achieves 92% conversion under identical conditions, as tracked by inline ReactIR. Process chemists utilizing continuous‑flow tubular reactors (PFA coil, 1.0 mm ID, residence time 45 min) have observed that pre‑activating the 5‑carboxylate acid chloride with N‑methylimidazole shifts the amidation endpoint to 98% within 2 h, a strategy adopted when the weaker intrinsic electrophilicity would otherwise stall kilo‑lab campaigns.

In a kilo‑lab setting at a contract manufacturing organization, the ester‑to‑amide conversion of methyl 2‑amino‑1,3‑thiazole‑5‑carboxylate via the intermediate acid (saponified with LiOH in THF/water 3:1 at 0 °C) was repeatedly compromised by residual lithium carboxylate aggregates that precipitated during DMF solvent swaps. These sub‑micron particulates blinded the 0.5 µm inline PTFE filters of the continuous stirred‑tank reactor train, causing back‑pressure excursions beyond 3.5 bar. The mitigation—switching to aqueous KOH and performing the saponification at 5 °C while monitoring pH statically at 12.0 ± 0.2—eliminated the gel‑like precipitate and permitted uninterrupted 48‑hour campaigns at 2.0 kg·batch⁻¹. This is a direct consequence of the 5‑carboxylate’s tendency to form stable chelates with hard cations, a behaviour markedly less pronounced in the ethyl ester variant where the longer alkyl chain disrupts carboxylate bridging.

Behavior of the amino‑thiazole core under reductive conditions in batch hydrogenation

The 2‑amino substituent is prone to partial hydrogenolysis on supported palladium catalysts if the exotherm is not tightly managed. Using a 5% Pd/C (type 39, sulfided) loading of 2.5% w/w relative to substrate, hydrogen uptake profiles at 3.0 barg and 35 °C revealed a two‑stage process: a rapid initial uptake corresponding to imine reduction of a trace Schiff‑base impurity formed during storage, followed by a slower plateau region representing the main substrate, which remained unchanged as confirmed by UPLC‑MS. The critical operational boundary is the temperature: beyond 45 °C, ring‑opening by‑products (detected as a m/z +18 adduct) appear with an onset at 48 °C in ethyl acetate, limiting the safe processing window to 35–40 °C. In contrast, the 4‑carboxylate isomer exhibits an exotherm onset for ring degradation 8 °C lower (37 °C) under otherwise identical conditions, making the 5‑carboxylate the preferred scaffold when downstream steps require catalytic hydrogenation upstream of a final deprotection.

Agrochemical intermediates derived from this scaffold—particularly N‑aryl amides prepared via EDCI‑mediated coupling with fluorinated anilines—are used as key building blocks for experimental succinate dehydrogenase inhibitor (SDHI) fungicide candidates. Structure–activity exploration has focused on the 5‑ester because the carboxylic acid function, once liberated, can be repositioned to interact with the conserved arginine residue of the SDH enzyme without the steric penalty imposed by the 4‑ester regioisomer, which forces the amide bond vector into an unfavourable torsion angle of +28° relative to the inhibitor pharmacophore plane (measured by X‑ray co‑crystal structures in published patent literature). The outcome is a 10‑ to 15‑fold improvement in IC₅₀ against Zymoseptoria tritici for the 5‑regioisomer series, a differentiation that directly drives demand specifications at the contract synthesis level where isomer‑free material (< 0.3% 4‑carboxylate by HPLC) is contractually required.

Details on physicochemical distinctions between ester homologues are consolidated in Table 2. The data were generated using the same analytical protocols applied to production batches.

Table 2 – Comparative data: Methyl, ethyl, and tert‑butyl 2‑amino‑1,3‑thiazole‑5‑carboxylates
Property	Methyl ester	Ethyl ester	tert‑Butyl ester
Melting range (°C)	167–169	148–150	122–124 (dec.)
Aqueous solubility (mg·L⁻¹, 25 °C, pH 6.8)	3200 ± 150	1800 ± 100	420 ± 30
Log P (octanol/water, shake‑flask)	0.78	1.35	2.12
Stability to acidic cleavage (HCl 2 N, dioxane, reflux)	Cleavage 98% in 6 h	Cleavage 95% in 8 h	Cleavage 100% in 2 h (with gas evolution)
Typical HPLC purity after recrystallization from toluene/MeOH	≥ 98.5%	≥ 99.0%	≥ 97.5%

When the tert‑butyl ester is considered as a protecting‑group strategy for the carboxylic acid, the thermal lability noted in Table 2 imposes strict temperature control during final‑stage coupling; operators on 200‑L glass‑lined vessels have reported exothermic decomposition events beginning at 82 °C with a self‑heating rate exceeding 2 °C·min⁻¹, which necessitates 0 °C quench protocols and the presence of a dedicated rupture disc rated to 1.0 barg. such practical constraints have led many kilo‑lab teams to revert to the methyl ester, accepting the slightly more vigorous saponification conditions (LiOH, THF/H₂O, 0 °C to room temperature over 16 h) in exchange for benign thermal handling.

Methyl 2‑amino‑1,3‑thiazole‑5‑carboxylate is stored in tightly sealed HDPE drums under nitrogen overlay; exposure to ambient humidity at RH > 60% for periods exceeding 48 h results in a water uptake of 0.8–1.2% w/w, which catalyzes ester hydrolysis during subsequent reactions performed in aprotic solvents. Karl Fischer titration should confirm ≤ 0.5% moisture before use in any palladium‑catalyzed cross‑coupling, as water contents above 0.7% suppress the turnover frequency of Pd(dba)₂/XPhos systems by approximately 40%, likely due to competitive hydration of the active catalyst species. Pharmaceutical customers filing drug master files under US FDA 21 CFR 314.420 routinely request a retest period of 12 months with storage at 2–8 °C, a practice supported by forced‑degradation studies showing < 0.2% total related substances after 12 months under these conditions.

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