1,3-Thiazole-2-Carboxylic Acid

Process Control Limits for Amide Bond Formation in Thiazole-Based API Intermediates

In multipurpose active pharmaceutical ingredient (API) manufacturing suites operated under 21 CFR Part 211 compliance, 1,3-thiazole-2-carboxylic acid is most frequently activated for amide bond formation using a carbodiimide/hydroxybenzotriazole system. A representative charge for a late-stage antiviral intermediate couples the heterocyclic acid with a sterically congested aliphatic amine in anhydrous N,N-dimethylformamide (DMF)–dichloromethane mixtures at a volumetric ratio of 3:1. The stoichiometry is deliberately skewed: the acid is held at 1.00 molar equivalent, while N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC·HCl) is introduced at 1.15±0.03 equivalents and 1-hydroxybenzotriazole hydrate (HOBt·H₂O) at 1.05 equivalents; the amine component is maintained at 1.02–1.08 equivalents to suppress homodimerization of the activated carboxylate. Because the thiazole ring nitrogen is susceptible to protonation-triggered side reactions at low pH, the internal batch pH is continuously monitored via an in-line Mettler Toledo InPro 3250i probe and buffered between 4.8 and 5.4 through controlled addition of N-methylmorpholine. Slow addition of a pre-cooled (−5°C) amine solution over 90–120 minutes under jacket temperature control at 0°C to +3°C limits the adiabatic temperature rise to below 8°C, as determined by reaction calorimetry performed on a Mettler Toledo RC1mx prior to scale-up. Quenching with dilute acetic acid (5% w/v) followed by phase separation and two organic washes with 2% sodium bicarbonate solution removes residual HOBt and urea by-products. The crude intermediate is crystallized from a ternary solvent system of ethyl acetate/n-heptane/tetrahydrofuran (7:2:1 v/v/v) with a cooling gradient from 55°C to −5°C at 0.15°C/min in a 316L stainless steel crystallizer equipped with a retreat-curve impeller. Isolated yield across campaigns typically ranges from 78 to 84% of theory when the water content of the reaction mass is held below 0.05% by Karl Fischer titration (Metrohm 870 KF Titrino plus) and the free amine is pre-dried over 4Å molecular sieves. A variant procedure applicable to thermally labile amines substitutes 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU) for EDC/HOBt in 0.95 equivalents, though this necessitates a subsequent ion-exchange chromatography step to remove hexafluorophosphate counterions from the final API. The resulting thiazole-2-carboxamide fragment is a key structural element in several oral anticoagulant and antifungal triazole pharmacophores. Final release testing of the isolated intermediate on an Agilent 1260 Infinity II HPLC system with a diode-array detector and a Waters XSelect CSH C18 column (3.5 μm, 4.6×150 mm) must demonstrate purity ≥99.0 area% at 254 nm. Monitored critical impurities include the thiazole-2-carboxylic acid starting residual (≤0.10%), the corresponding symmetrical anhydride (≤0.15%), and isomeric carboxamide formed through ring nitrogen attack (Ph. Eur. 2.2.29). Genotoxic impurity control follows the ICH M7(R1) framework; a purge factor calculation based on the DEREK Nexus (v6.2.0) in silico prediction and spiking studies on the isolation train confirms that the process reduces any theoretically alkylating species below the threshold of toxicological concern of 1.5 μg/day. Residual solvent analysis conforms to ICH Q3C(R8), with headspace gas chromatography (Agilent 7697A/7890B dual-channel system) quantifying DMF below 880 ppm and dichloromethane below 600 ppm. Equipment train: the reaction is executed in a 500 L glass-lined reactor (Pfaudler AE series) with a Hastelloy C-22 overhead condenser, post-reaction neutralization performed in an intermediate receiver, and isolation completed on a Nutsche filter–dryer (Mavag AG) under inert gas blow-down. Single-crystal X-ray diffraction (Bruker D8 Venture) of retained reference batches confirms the Z-conformation of the amide bond, a conformational preference critical for receptor docking.

In dedicated agrochemical synthesis suites, the conversion of 1,3-thiazole-2-carboxylic acid to its acid chloride with thionyl chloride generates a corrosive off-gas stream that must be scrubbed through a dual-stage packed column containing dilute 15% w/w sodium hydroxide and activated carbon before venting. The charge ratio is 1.00 kg of the acid (MW 129.14 g/mol, typically at 98.5% assay) to 2.6–2.8 molar equivalents of redistilled thionyl chloride, with N,N-dimethylformamide added as a reaction initiator at 0.3% w/w relative to substrate. Reflux is maintained at 72–76°C under a nitrogen blanket for 6–8 hours until evolution of hydrogen chloride and sulfur dioxide ceases, as signaled by a plateau in the conductivity drop across the scrubber liquor. Excess sulfoxyl chloride is stripped via vacuum distillation (100 mbar, jacket 55°C) to a residual level ≤0.2% by GC-FID. The resulting pale-yellow liquid 1,3-thiazole-2-carbonyl chloride is employed directly, without purification, in a Schotten-Baumann condensation with a substituted aniline dissolved in dichloromethane and aqueous sodium bicarbonate (10% w/w) at 0–5°C using a 0.2% w/w tetrabutylammonium bromide phase-transfer catalyst relative to amine. An operational boundary of pH 8.0–8.3 is enforced to minimise hydrolysis of the acyl chloride while suppressing ring opening of the thiazole nucleus; deviations outside this window cause an immediate increase in the 2-aminothiophenol by-product, monitored by TLC on silica gel 60 F₂₅₄ (hexane:ethyl acetate 3:1). The resulting thiazole-2-carboxanilide, after neutralization and recrystallization from ethanol/water, serves as the core scaffold for broad-spectrum foliar and seed-treatment fungicides with activity against Rhizoctonia solani and Botrytis cinerea. Formulation into suspension concentrates (SC, 480 g/L a.i.) or water-dispersible granules (WG) must comply with FAO Specification 58.5/EC for wettability and suspensibility as determined by CIPAC MT 184. Residue trials for Codex Alimentarius maximum residue limit (MRL) establishment are conducted on grapes and tomatoes with a limit of quantification of 0.01 mg/kg. REACH registration under Regulation (EC) No 1907/2006 Title II demands a chemical safety report covering aquatic toxicity (Daphnia magna EC₅₀ 48 h > 100 mg/L) and ready biodegradability (OECD 301B). The entire synthesis train is constructed from boron silicate glass-lined steel (Pfaudler WWG) with PTFE gaskets and is interlocked to shut down the SOCl₂ feed pump if the reactor pressure exceeds 0.5 bar(g).

Can Solid-Phase Peptide Synthesis Tolerate Unprotected Thiazole Carboxylic Acids?

The direct incorporation of 1,3-thiazole-2-carboxylic acid onto the N-terminus of a resin-bound peptide without prior protection of the ring nitrogen has been evaluated on a CS Bio CS336X automated synthesizer using standard Fmoc/tBu chemistry. The resin substitution must be kept below 0.45 mmol/g on aminomethyl polystyrene cross-linked with 1% DVB to minimize on-resin interchain aggregation driven by the heteroaromatic dipole. Activation is performed with 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HBTU, 0.95 equiv relative to acid) and 1-hydroxybenzotriazole (HOBt, 0.95 equiv) in peptide-synthesis-grade DMF, with the acid dissolved at a concentration of 0.18 M. The coupling cocktail is pre-activated for 4–5 minutes at 0°C before being delivered to the drained resin. Double couplings of 45 minutes each at 25°C are required to achieve a Kaiser-negative (≤1% residual free amine by TNBS quantitation on a small resin aliquot using a Thermo Scientific NanoDrop One UV-Vis at 335 nm). A critical processing note is the exclusion of oxygen from the reaction vessel headspace: the thiazole sulfur atom is susceptible to oxidation to the corresponding sulfoxide during extended base exposure, and a continuous nitrogen sweep (0.2 L/min) through the reaction vessel manifold is maintained throughout the coupling cycle. After iterative Fmoc deprotection with 20% piperidine in DMF (2×5 min), the full-length peptide is cleaved from the resin with trifluoroacetic acid/triisopropylsilane/water (95:2.5:2.5 v/v/v) at 22°C for 3 hours, followed by precipitation in cold diethyl ether and preparative reversed-phase HPLC (Waters AutoPurification system, XBridge BEH C18 OBD, 10 μm, 19×250 mm, acetonitrile/water/0.1% TFA). The target peptide bearing the thiazole-2-carbonyl cap is obtained with overall 58–62% isolated yield relative to resin loading. Such peptides are developed as early-stage probes in fragment-based drug discovery targeting protein–protein interaction interfaces, particularly bromodomain and PDZ domain inhibitors. Because the material is produced under non-GMP conditions for biochemical screening, the purity specification is relaxed to ≥95% by LC-UV (214 nm), with full characterization by high-resolution mass spectrometry (Bruker maXis II ESI-QTOF) and ¹H-¹³C HSQC NMR. Potential process-related impurities include the dehydrated nitrile derivative formed at pH>9 and the oxazolone rearrangement product when HATU is substituted without pre-activation; both are tracked through a partial validation following ICH Q2(R1) for specificity and limit of detection even in research-grade campaigns. Scale-up beyond 50 mmol resin loading introduces an exotherm during pre-activation that cannot be adequately controlled in a jacketed glass reactor with a magnetic coupling, and therefore published data for this specific configuration is limited to batch sizes below 2 litre total volume.

A recurring deviation logged during solventothermal preparation of Cu(II)-thiazole metal-organic framework (MOF) involves nucleation lag times exceeding 6 hours when the cooling ramp deviates by more than 2°C/min from the validated profile. The mother liquor formulation combines copper(II) nitrate trihydrate with 1,3-thiazole-2-carboxylic acid at a molar ratio of 1:2.05 in a mixed solvent of N,N-dimethylformamide, absolute ethanol, and deionized water (4:4:2 v/v/v). An aliquot of concentrated nitric acid is titrated to adjust the initial pH to 3.3±0.2, protonating the carboxylate slowly to moderate the precipitation kinetics. The Teflon-lined autoclave (Parr Instrument Company, 125 mL capacity, model 4748) is heated from ambient to 85°C at 0.8°C/min, held isothermally for 24 h, and then cooled to 25°C at a controlled rate of 0.3–0.5°C/min. Deviations caused by ambient laboratory draughts or voltage fluctuations in mantle heaters have been traced to the formation of an amorphous phase co-existing with the targeted paddle-wheel secondary building unit; this amorphous contaminant is detectable as a broad halo in the baseline of the powder X-ray diffractogram (Bruker D2 Phaser, Cu Kα) between 8° and 14° 2θ. Induction of nucleation can be reliably shortened to 2–3 hours by seeding with 0.5% w/w of previously synthesized single crystals ground to <20 μm particle size and introduced at 72°C during the heating ramp. Activation of the as-synthesised framework proceeds via solvent exchange with anhydrous acetone over 72 h (fresh solvent every 12 h), followed by evacuation using a Micromeritics Smart VacPrep with a degas protocol of 24 h at 120°C and 10⁻⁴ mbar. The resulting Brunauer–Emmett–Teller surface area, measured on a Micromeritics 3Flex 3500 with nitrogen at 77 K and fitted according to ISO 9277:2010 over the 0.05–0.20 P/P₀ range, varies from 815 to 1,120 m²/g depending on the ramp rate history, with a total pore volume of 0.42–0.55 cm³/g. This copper-thiazole network has been examined as a heterogeneous catalyst for the click reaction between benzyl azide and phenylacetylene in toluene at 60°C, where induction time inversely tracks the percentage of open metal sites accessible after activation. Toxicological assessment of the precursor solution in contact with the MOF product requires inductively coupled plasma optical emission spectrometry (Agilent 5110 ICP-OES) analysis of copper leaching under simulated physiological conditions (phosphate-buffered saline, pH 7.4, 37°C, 72 h), with values ≤2.5 ppm routinely achieved.

When the Carboxyl Group Activates for Naphthalimide Chromophore Conjugation

1,3-Thiazole-2-carboxylic acid has been employed as a π-extending conjugate partner for the synthesis of 4-amino-1,8-naphthalimide-derived thiol-reactive fluorescent probes. The synthetic sequence departs from a 4-piperazinyl-1,8-naphthalic anhydride core dissolved in dry tetrahydrofuran under argon. The heterocyclic acid (1.3 equiv) is converted beforehand to the corresponding acid chloride using oxalyl chloride (1.8 equiv) with a catalytic quantity of DMF (0.1 mol%) in dichloromethane at 0°C, with the excess oxalyl chloride and solvent removed on a rotary evaporator at 30°C and 40 mbar. The freshly prepared acyl chloride is taken up in 5 mL anhydrous THF and added dropwise over 25 minutes to the naphthalimide amine solution containing anhydrous triethylamine (2.5 equiv) held at −10°C in an acetone-dry ice slush bath under yellow light to prevent photoinduced electron transfer. After warming to ambient temperature over 4 h, the reaction is quenched with ice-cold 1.0 M HCl and the product extracted into ethyl acetate. Chromatography on silica gel 60 (particle size 40–63 μm) with a gradient from 20% to 45% ethyl acetate in hexane isolates the desired thiazole-2-carboxamidonaphthalimide as a pale orange solid. Spectroscopic characterization in 10 mM phosphate buffered saline (pH 7.4) containing 1% DMSO reveals an absorption maximum at 413±3 nm and an emission maximum at 535±5 nm upon excitation at 405 nm, with an absolute fluorescence quantum yield of 0.48±0.04 determined using a Hamamatsu C9920-02G integrating sphere system. The terminal succinimidyl ester derivative reacts with free thiols of reduced glutathione with a second-order rate constant on the order of 10³ M⁻¹s⁻¹ at 37°C. In live-cell confocal microscopy (Leica TCS SP8, ×63 oil immersion objective, HeNe laser 405 nm), the probe accumulates in the endoplasmic reticulum of HeLa cells within 15 min of incubation at 2 μM and remains non-cytotoxic at concentrations up to 20 μM as judged by an MTT reduction assay performed per ISO 10993-5:2009 guidelines. For commercial shipment of such probes, the bulk powder must be sealed under argon in amber glass vials and certified for residual solvent levels: THF ≤720 ppm, dichloromethane ≤600 ppm, and ethyl acetate ≤5000 ppm, in line with ICH Q3C option 2 limits. Published data for the photobleaching half-life under continuous irradiation (Xe lamp, 450 W) in aerobic aqueous solution is limited, though preliminary assessments indicate signal degradation of ≤15% over 60 minutes under standard imaging conditions.

Examination of immersion plating baths for horizontal organic solderability preservative (OSP) lines indicates that partially neutralized 1,3-thiazole-2-carboxylic acid, combined with a small fraction of formic acid, deposits a homogeneous complex film on copper pads at conveyor speeds ranging from 0.8 to 1.4 m/min. The active bath is prepared by dissolving 8–12 g/L of the solid acid in deionized water at 50°C and adjusting the pH to 4.0–4.3 with a 0.5 M sodium acetate/acetic acid buffer system, followed by addition of 0.3–0.8 g/L of 85% formic acid as a co-complexant to improve film thickness uniformity across circuit features ranging from 80 μm pitch BGAs to large ground planes. The immersion bath temperature is held at 47±2°C via an in-line quartz heater with PID feedback, and the contact time—controlled by the conveyor dwell zone length of 2.2 m—stays within 50–70 seconds. Post-deposition, the film is rinsed in two successive deionized water cascades (conductivity <5 μS/cm) and dried by an air knife set to 0.55 MPa air pressure. X-ray fluorescence thickness measurements (Fischerscope X-RAY XDLM 237) on 25 μm×25 μm test pads yield dry film thicknesses of 0.18–0.42 μm, meeting the Type A OSP requirements of IPC-4552A. Solderability verification against J-STD-003B Category 3 demonstrates wetting balance force above 300 μN after a single lead-free reflow simulation and 48 h of steam aging at 93°C and 95% relative humidity. An in-process copper mirror corrosion test per IPC-TM-650 Method 2.6.15 is conducted every 4 h of production: a glass slide with vacuum-deposited copper (200 nm) is immersed in the bath for 5 min and any colour shift beyond a Munsell 5YR 7/4 reference triggers immediate dump and recharge. Published data for this specific thiazole-carboxylic acid configuration in mixed-metal assemblies (gold wire bonding on OSP-coated pads) is limited, and users are cautioned to validate wire pull strength per MIL-STD-883 Method 2011.9 before committing to volume production. Immersion bath life is typically 120–140 panel area turnovers per litre of concentrate before copper build-up exceeds 2,500 ppm and necessitates a carbon adsorption polishing step. The bath is fully discharged as non-halogenated organic waste at pH 6–8 after neutralization, with local discharge limits for copper ≤2.0 mg/L verified by atomic absorption spectrophotometry.

1,3-Thiazole-2-carboxylic acid (CAS 40853-56-1, C₄H₃NO₂S, molecular weight 129.14 g·mol⁻¹) is supplied as a white to off‑white crystalline powder with a melting range of 102–106 °C (USP ⟨741⟩). Routine quality control combines reversed‑phase HPLC for purity assessment (C18 column, 250 × 4.6 mm, 5 µm; phosphate buffer pH 2.5/acetonitrile gradient; UV detection at 254 nm) and Karl Fischer coulometry (ASTM E203) to cap moisture at ≤0.5 %. Loss on drying (105 °C, 2 h) is held to ≤0.3 %, and sulfated ash (USP ⟨281⟩) remains below 0.1 %. The compound is soluble in dimethylformamide, dimethyl sulfoxide, and warm ethanol; it forms clear solutions at 50 mg·mL⁻¹ in DMF dried over 4 Å molecular sieves. The free acid and its hydrochloride salt serve as compact heterocyclic building blocks for medicinal chemistry campaigns, agrochemical discovery, and ligand synthesis.

What Differentiates the 2‑Carboxyl Regioisomer from Its 4‑ and 5‑Position Counterparts in Amide Bond Formation?

Placing the carboxylic acid at the 2‑position places it adjacent to both the ring sulfur and the endocyclic nitrogen, generating a steric environment more congested than that of the 4‑ or 5‑isomers. This spatial constraint alters activation kinetics: when 1,3‑thiazole‑2‑carboxylic acid is converted to an active ester with HOBt/EDC in anhydrous DMF at 0–5 °C, complete pre‑activation typically requires 60–90 min, approximately 20–30 min longer than the 4‑isomer under identical conditions. Coupling yields with sterically demanding amines (e.g., tert‑butylamine) can be 5–15 % lower than the 4‑carboxy variant when a one‑pot protocol is employed; addition of the amine before full O‑acylisourea formation raises the proportion of the symmetric anhydride side product detectable by LC‑MS at m/z 237 [M + H]⁺. For bulky nucleophiles, superior conversions are obtained with the uranium‑type activator HATU and 2,4,6‑collidine in DMF, yielding the corresponding amide with >85 % conversion after 16 h at ambient temperature. Systematic comparative datasets across all three regioisomers remain sparse in the open literature; however, the trend of slower acylation in the 2‑series is consistent with computed steric shielding and is regularly observed during kilogram‑scale campaigns in pilot plants equipped with 100‑L glass‑lined reactors.

Comparative Activation Behaviour of Thiazole Carboxylic Acid Regioisomers with EDC/HOBt
Parameter	1,3‑Thiazole‑2‑carboxylic acid	1,3‑Thiazole‑4‑carboxylic acid	1,3‑Thiazole‑5‑carboxylic acid
Typical half‑life for active ester formation^a	35‑45 min	15‑20 min	20‑25 min
Side‑product risk with 2‑equiv. DCC	N‑acylurea (Δm +98 Da)	Symmetric anhydride dominant	Symmetric anhydride dominant
Recommended pre‑activation temperature	‑5 to 0 °C	0–5 °C	0–5 °C
Coupling yield with n‑propylamine (HATU/DIEA)	88–94 %	95–99 %	93–98 %
Enantiomeric purity retention in dipeptide model^b	>99.5 % ee	>99.5 % ee	98–99 % ee

^a In‑situ IR monitoring of the carbonyl stretch at 1805 cm⁻¹. ^b Chiral HPLC with Chiralpak IA‑3 column, hexane/ethanol 80:20; racemization from oxazolone intermediate is more pronounced in the electron‑poor 5‑isomer.

Pharmaceutical Intermediate Quality: Specification Benchmarks and Analytical Rigor

For use as a regulatory starting material (ICH Q7), the carboxylic acid is released against a comprehensive certificate of analysis. Typical purity by HPLC area‑percent (detection at 254 nm) exceeds 98.5 %, with individual unspecified impurities capped at ≤0.10 %. The main potential contaminant—unreacted thiazole precursor or regioisomeric acid arising from carboxylation side‑reactions—is tracked at a reporting threshold of 0.05 %. Residual N,N‑dimethylformamide and ethanol from recrystallization are determined by headspace GC‑FID following USP ⟨467⟩; limits are set at ≤880 ppm and ≤5000 ppm, respectively. Water content via coulometric Karl Fischer (USP ⟨921⟩, Method Ia) must not exceed 0.5 %, as moisture accelerates hydrolysis of the carboxylic acid to 2‑aminothiazole at temperatures above 40 °C. For GMP‑grade material destined for parenteral drug substance synthesis, an additional inductively coupled plasma mass spectrometry screen (USP ⟨233⟩) controls lead ≤10 ppm, cadmium ≤2 ppm, and mercury ≤3 ppm. Identity is confirmed by FT‑IR matching the carbonyl stretch at 1685 ± 5 cm⁻¹ and by ¹H NMR in DMSO‑d₆ showing the two thiazole ring protons as doublets at δ 8.09 and δ 7.98 (J = 3.2 Hz). The product carries a retest period of 24 months when stored at 2‑8 °C under dry nitrogen in light‑resistant HDPE containers.

Handling at production scale requires moisture exclusion. Opening of containers on the shop floor is performed inside a dry nitrogen‑purged glove bag when ambient relative humidity exceeds 60 %. For moisture‑sensitive coupling reactions in peptide synthesis, the acid is pre‑dried in a vacuum oven at 40 °C (‑0.08 MPa) for 4 h immediately before use. The compound is incompatible with strong oxidizing agents (e.g., nitric acid, peroxides) and should never be blended with amine‑based additives in the absence of solvent, as exothermic salt formation can generate local hot spots exceeding 120 °C, triggering decarboxylation. Solutions in DMF or DMSO are stable for ≤8 h at 20 °C; prolonged storage leads to formation of a red‑brown oxidation product that absorbs at 340 nm and interferes with subsequent HPLC control.

Metal‑Catalyzed Functionalization of the Thiazole Core and the Influence of the 2‑Carboxylic Acid Group

The electron‑withdrawing nature of the carboxyl moiety deactivates the ring toward electrophilic substitution, but it markedly facilitates palladium‑catalyzed cross‑coupling at the 5‑position when the acid is converted to a directing Weinreb amide. Optimised Buchwald‑Hartwig protocols use Pd₂(dba)₃ (2 mol %) and Xantphos (4 mol %) in degassed 1,4‑dioxane at 100 °C with K₃PO₄ as base, delivering 5‑arylated products with isolated yields of 72–89 % after silica gel chromatography. Attempts to perform direct Suzuki–Miyaura coupling on the free acid often give 10–20 % conversion due to competing protodecarboxylation catalyzed by the aqueous base; therefore, pre‑esterification to the methyl or benzyl ester is strongly advised. The resulting 5‑substituted 2‑carboxylate esters serve as advanced intermediates for kinase inhibitor scaffolds where the 2‑carboxy unit mimics the pyrazole‑carboxylic acid pharmacophore found in several marketed anti‑inflammatory agents. Pilot‑plant batches using 10‑L jacketed reactors with overhead stirring have demonstrated consistent product distributions (±2 % yield variation across five consecutive lots), provided that the dissolved oxygen level in dioxane is reduced to ≤5 ppm by sparging with argon prior to catalyst addition.

When Selecting a Thiazole Building Block for Parallel Library Synthesis

Choice between the 2‑carboxylic acid and the isomeric 4‑carboxylic acid analogue often turns on the desired electronic profile and steric tolerance of the downstream diversification step. The 2‑carboxy compound places the electron‑withdrawing group directly adjacent to the C=N bond, lowering the LUMO energy by approximately 0.3–0.5 eV compared with the 4‑isomer, as estimated from DFT studies with the B3LYP/6‑31G(d) basis set. This enhanced electrophilicity accelerates nucleophilic aromatic substitution at the 5‑position, making it the preferred scaffold when installing alkyl‑ or arylamines under microwave irradiation (150 °C, 30 min). Conversely, if the synthetic plan requires Heck‑type coupling at the 4‑position (which is blocked in the 4‑carboxy isomer), the 2‑carboxy derivative is mandatory. Combinatorial chemistry groups operating automated liquid handlers (e.g., Tecan Freedom EVO®) report that the free acid’s solution stability in DMSO‑d₆ limits maximum library plate storage to 72 h at ‑20 °C after which around 3 % decomposition is detectable. Switching to the corresponding methyl ester, which can be hydrolysed post‑library synthesis, circumvents this shelf‑life constraint. Patent literature exemplifies the 2‑carboxylic acid as a key synthon in the preparation of thrombin inhibitors (e.g., dabigatran precursors) and factor Xa antagonists, where the thiazole core contributes to a binding pK_i improvement of 0.5–1.0 log units over the oxazole analogue.

On multi‑purpose fine‑chemical trains, the recovery of excess 1,3‑thiazole‑2‑carboxylic acid from aqueous quench streams is complicated by its pK_a of ~2.9 (carboxyl) and the pK_a of the protonated thiazole ring near ‑0.5. Liquid‑liquid extraction into ethyl acetate is efficient only when the aqueous phase is adjusted to pH ≤1.0 with sulfuric acid, a condition that requires corrosion‑resistant Alloy C‑276 centrifugal extractors. Process safety evaluations conducted with an ARC calorimeter (ASTM E1981) indicate a decomposition onset temperature of 215 °C with a maximum self‑heat rate of 1.8 °C·min⁻¹ at 257 °C, placing the drying and packaging operations well outside the criticality range under standard thermal controls. Implementation of these engineering boundaries allows supply of the product in 25‑kg fibre drums with a documented transportation classification of Non‑regulated.

HS Code	675963
Name	1,3-Thiazole-2-Carboxylic Acid
Molecular Formula	C4H3NO2S
Molecular Weight	129.14 g/mol
Appearance	Solid
Melting Point	159 - 163 °C
Solubility In Water	Slightly soluble
Solubility In Organic Solvents	Soluble in some organic solvents like ethanol
Pka Value	Approx. 2.6
Density	1.54 g/cm³
Odor	Odorless

Packing	100g of 1,3 - Thiazole - 2 - Carboxylic Acid packaged in a sealed plastic bag.
Shipping	1,3 - Thiazole - 2 - Carboxylic Acid is shipped in well - sealed, corrosion - resistant containers. Shipment adheres to strict chemical transport regulations, ensuring proper handling to prevent spills and maintain product integrity during transit.
Storage	1,3 - Thiazole - 2 - Carboxylic Acid should be stored in a cool, dry, well - ventilated area. Keep it away from sources of heat, ignition, and incompatible substances such as strong oxidizing agents. Store in a tightly sealed container to prevent moisture absorption and potential degradation. Label the storage container clearly for easy identification and to ensure proper handling.