2-Thiazolecarboxaldehyde
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HS Code |
416058 |
| Chemical Formula | C4H3NOS |
| Molar Mass | 113.14 g/mol |
| Appearance | Colorless to light yellow liquid |
| Boiling Point | 198 - 200 °C |
| Melting Point | N/A |
| Density | 1.24 g/cm³ |
| Solubility In Water | Slightly soluble |
| Odor | Pungent |
| Flash Point | 83 °C |
| Refractive Index | 1.587 - 1.591 |
| Stability | Stable under normal conditions |
As an accredited 2-Thiazolecarboxaldehyde factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 20 - gram vial of 2 - Thiazolecarboxaldehyde, securely sealed in a chemical - resistant package. |
| Shipping | 2 - Thiazolecarboxaldehyde is shipped in sealed, corrosion - resistant containers. Special care is taken to prevent leakage during transit, following strict chemical shipping regulations to ensure safety of handlers and the environment. |
| Storage | 2 - Thiazolecarboxaldehyde should be stored in a cool, dry, well - ventilated area, away from heat sources and ignition sources. Keep it in a tightly sealed container to prevent evaporation and contact with air and moisture, which could lead to decomposition or reactions. Store separately from oxidizing agents and incompatible substances to avoid potential hazardous reactions. |
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Production-scale manufacture of the antiparasitic agent nitazoxanide requires multi-ton quantities of 2-amino-5-nitrothiazole, a core heterocyclic building block. A robust supply chain relies on 2-Thiazolecarboxaldehyde as the primary aldehyde input for the oxime formation–reduction–nitration sequence. In a typical campaign, 1500 kg of the aldehyde is charged into a 5000 L glass-lined reactor equipped with a retreat-curve impeller. Hydroxylamine hydrochloride (1.05 molar equivalents) dissolved in reverse-osmosis water is added dropwise while maintaining the jacket at −5 °C to 0 °C. The pH is adjusted to 4.8–5.2 with 30% w/w sodium carbonate solution, and the suspension is held for 4 h. The resulting 2-thiazolecarboxaldehyde oxime is isolated via a bottom-discharge centrifuge, washed with chilled deionized water until the filtrate chloride content drops below 50 ppm, and dried at 40 °C under 80 mbar vacuum. Typical yield: 94–96% with a melting point of 98–100 °C. The wet oxime cake is then reduced with zinc dust (2.2 equiv) in 85% formic acid at 60 °C, affording 2-aminothiazole after neutralization and toluene extraction. The amine is nitrated using mixed acid (HNO3/H2SO4 = 30/70 v/v) at –5 °C ± 2 °C, with careful kinetic controls to avoid exothermic runaway; the dinitro impurity must stay below 0.30% area by HPLC. Final recrystallization from isopropanol/acetone (4:1 v/v) yields 2-amino-5-nitrothiazole conforming to USP monograph specifications: purity ≥99.5%, water by Karl Fischer ≤0.3%, sulfated ash ≤0.1%, and single unknown impurity ≤0.10%. Operational boundaries are stringent: the oxime photo-degrades under fluorescent lighting, requiring amber-coated lamps and light-exclusion piping. Residual hydroxylamine in the centrate must be quenched with acetone before biotreatment. REACH registration dossier includes an OECD 301B ready biodegradability study confirming <20% degradation in 28 days, necessitating dedicated activated-carbon polishing of effluent. The nitro-thiazole intermediate is subsequently acylated with acetylsalicylic acid chloride and coupled with 2-mercaptobenzothiazole to obtain nitazoxanide meeting ICH Q3A thresholds for genotoxic impurities. Suppliers adhering to EXCiPACT certification or holding an active CEP (Certificate of Suitability to the European Pharmacopoeia) are preferred. What control measures prevent Knoevenagel by-product formation at pilot scale?Within the agrochemical discovery pipeline, 2-Thiazolecarboxaldehyde serves as the electrophilic anchor for constructing α,β-unsaturated cyanoesters that eventually feed into ALS-inhibiting herbicides. The Knoevenagel condensation with ethyl cyanoacetate is performed in toluene (6 volumes relative to aldehyde weight) with a catalytic mixture of piperidine (0.05 equiv) and glacial acetic acid (0.04 equiv). The aldehyde (1.00 mol) and ethyl cyanoacetate (1.02 mol) are charged into a jacketed glass-lined vessel; the overhead Dean–Stark trap is filled with molecular sieve 4A beads. Rapid heating to reflux (111 °C) drives azeotropic removal of water, and the endpoint is monitored by GC—residual aldehyde must fall below 0.5% area before cooling. A persistent challenge at 200 L pilot scale has been the formation of a viscous by-product identified as the Michael adduct dimer when localized overheating occurs around the steam tracing. Mitigation requires a retreat-blade glass-lined agitator running at 110–130 rpm and an internal coil that limits the temperature rise to 3 °C/min during the heat-up ramp. The reaction mass is cooled to −5 °C over 6 h to crystallize ethyl 2-cyano-3-(thiazol-2-yl)acrylate, which is filtered, washed with cold toluene, and dried under nitrogen purge at 35 °C. Typical yield: 87–91%, with a purity by GC-FID of 98.5% minimum and a melting point of 74–76 °C. The intermediate is hygroscopic and must be stored in heat-sealed aluminum-laminate bags with a desiccant sachet; moisture uptake above 0.3% causes rapid decomposition during the subsequent hydrogenation step. The hydrogenation to the saturated propanoate utilises Raney nickel at 3 bar hydrogen pressure in ethanol, a step validated per ASTM E2884 for oxygen exclusion. Final herbicide actives—typically formulated as suspension concentrates or water-dispersible granules—undergo inert ingredient screening in accordance with EPA 40 CFR § 180.910. Process vent condensers are sized for toluene capture with 99% recovery to meet local VOC emission limits, and waste water is stripped to <0.1 mg/L cyanide before discharge. Stoichiometric generation of 2-thiazolidinethiones in Maillard-type reaction flavor basesThermal process flavorists utilise 2-Thiazolecarboxaldehyde as a precursor to sulfurous roast and meat aroma volatiles formed through Strecker-dependent pathways. In a standard reaction flavor base destined for a beef top-note concentrate, the aldehyde (1.00 mol) is combined with L-cysteine hydrochloride monohydrate (1.20 mol), D-glucose (0.15 mol), and sodium chloride (0.05 mol) in demineralized water (10 parts per part aldehyde). The slurry is heated in a steam-jacketed pressure vessel with a full-diameter magnetic-drive agitator. Temperature is ramped to 118 °C over 45 min and held for 90 min; the internal pressure reaches 1.8 bar. pH is continuously monitored through a hot-lapped ceramic probe and maintained at 6.2–6.5 via programmed addition of 1.0 M sodium hydroxide solution. The key volatile markers—2-thiazolidinethione and 2-methylthiazole—are tracked by inline headspace sampling with a fast-GC detector. The reaction is quenched by passing the mass through a tube-in-tube cooler, reducing the temperature to 30 °C within 3 min. The resulting brown paste contains <2 ppm residual free aldehyde, confirmed by ISO 22119 extraction and GC-MS. Equipment cleaning protocols rely on hot 0.5% w/w sodium hydroxide circulation, as the flavor residue polymerizes on stainless-steel walls after 24 h of standstill. The flavor base is standardized with maltodextrin to a moisture content of 5.0 ± 0.3% and marketed as a “processed flavor” compliant with EU Regulation 1334/2008/EC. Users incorporating it into savory snacks must list it as “flavoring” and ensure the finished product’s thiazole volatile profile does not exceed the organoleptic perception threshold of 0.8 μg/m³ in air, as evaluated by ASTM E679 panel tests. When the formyl group is converted to its primary amine through catalytic amination, the resulting chromophore exhibits higher wash fastness on polyesterDisperse dye chemists exploit 2-Thiazolecarboxaldehyde as a source of 2-aminomethylthiazole, a heavy diazo component that shifts the hue of monoazo colorants bathochromically. In a dedicated multi-purpose fine-chemicals plant, the aldehyde (1.0 kmol) is dissolved in methanol (4 volumes) and charged into a 500 L Hastelloy C-276 hydrogenation autoclave. Ammonia gas is sparged at 15 °C until the molar ratio reaches 3.5:1 relative to aldehyde, followed by addition of Raney nickel slurry (2.5% w/w wet catalyst). The reactor is pressurized to 3.0 MPa with hydrogen and heated to 80 °C; agitation is maintained at 800 rpm using a gas-inducing impeller. The amination proceeds with an expiring hydrogen flow until an inline FT-IR probe records the disappearance of the carbonyl band at 1706 cm⁻¹. After filtration through a 2 μm sintered-metal filter candle, the methanolic solution of crude 2-aminomethylthiazole (88–92% yield by nonane internal standard) is distilled under vacuum to a concentration of 40% actives. For diazotization, the amine concentrate is acidified with 36% w/w hydrochloric acid at 0–5 °C and treated with sodium nitrite (1.01 equiv). Excess nitrous acid is quenched with sulfamic acid, and the diazonium salt solution is rapidly coupled with N,N-diethylaniline (0.98 equiv) in an acetic acid-sodium acetate buffer at pH 4.5. The coupling slurry is filter-pressed, washed to conductivity <100 μS/cm, and dried in a conical screw dryer under 60 °C. The resulting C.I. Disperse Red 359 analog (generic designation) exhibits a molar extinction coefficient of 3.2 × 10⁴ L·mol⁻¹·cm⁻¹ at λmax 512 nm in DMF. High-temperature exhaust dyeing on polyester fabric at 130 °C for 45 min yields a color strength 95% of the reference standard when tested per ISO 105-C06 C2S. Wash fastness after three cycles meets 4–5 rating on the grey scale. The powdery dye is standardized to 33.0 ± 0.5% coloring strength with lignosulfonate dispersants. Residual formaldehyde in the final dye powder, measured by JIS L 1041 method B, must not exceed 16 mg/kg to qualify for OEKO-TEX Standard 100 product class I. Under strictly anhydrous Schlenk techniques, 2-Thiazolecarboxaldehyde condenses with (1R,2R)-cyclohexane-1,2-diamine to afford a tetradentate N,N′-bis(2-thiazolylmethylene)cyclohexanediamine ligand. This C2-symmetric framework, when metalated with manganese(II) acetate tetrahydrate, generates an epoxidation catalyst deployed in the asymmetric synthesis of chiral epoxy alcohols for fragrance intermediates. The condensation is executed in dry dichloromethane (2 L per mole diamine) over activated 3A molecular sieves. Aldehyde (2.20 mol) is added dropwise to the diamine (1.00 mol) at reflux, and the reaction is driven to completion by monitoring the imine C=N stretch at 1635 cm⁻¹ with an attenuated total reflectance probe. After 18 h, the sieves are removed, and the yellow solution is concentrated under 40 mbar at 25 °C. The crude ligand is recrystallized from anhydrous ethyl acetate/hexane (1:3 v/v) inside a glovebox (H2O <0.1 ppm, O2 <0.2 ppm). Yield: 79% of bright yellow microcrystals, melting point 142–144 °C (decomposition). Scale-up beyond 5 L total volume requires a jacketed vessel with a Pfaudler blue-glass lining; the exotherm during aldehyde addition mandates a subsurface feed and a minimum jacket cooling capacity of 150 W·L⁻¹·K⁻¹. The metalated catalyst is generated in situ by stirring a 0.5 M methanolic ligand solution with manganese(II) acetate (1.0 equiv) in the presence of air, forming an oxo-bridged dimer. This catalyst achieves enantiomeric excesses of 89–92% for the epoxidation of styrene substrates using 3.0 equiv of 30% aqueous hydrogen peroxide as terminal oxidant, according to chiral GC method ASTM D7574. The ligand itself must be tested for residual palladium (from a prior cross-coupling step in some integrated routes) by ICP-OES; a specification of <1 ppm Pd is enforced when the resulting epoxide enters pharmaceutical intermediates under ICH Q3D elemental impurity guidelines. Any deviation in crystalline morphology—visible as amorphous agglomerates under polarized light—indicates moisture ingress and is cause for batch rejection, as water promotes aldol self-condensation of the aldehyde and reduces ligand diastereomeric purity to below 97% de.
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Aromatic heterocyclic aldehydes bearing endocyclic nitrogen and sulfur atoms serve as critical intermediates in the convergent synthesis of pharmaceutical actives, agrochemicals, and flavour constituents. 2-Thiazolecarboxaldehyde (CAS 10200-59-6; IUPAC 1,3-thiazole-2-carbaldehyde; molecular formula C₄H₃NOS; molecular weight 113.14 g·mol⁻¹) is the 2-formyl derivative of thiazole, a five-membered 1,3-azole possessing both a soft sulfur donor and a basic imine-type nitrogen. The aldehyde moiety is directly attached to the C2 position of the ring, placing the formyl carbon under the electron‑withdrawing influence of both the sulfur and the C=N unit, which profoundly modulates its reactivity toward nucleophiles, oxidants, and transition-metal catalysts compared to its regioisomers and to oxygen‑ or sulfur‑only heterocyclic carbaldehydes. Commercially, the substance is supplied as a pale‑yellow to amber liquid that crystallizes at temperatures below 5–7 °C, with purity grades ranging from 95 % (technical, stabilised with 0.1 % hydroquinone) to ≥ 99.5 % (pharmaceutical intermediate, sublimed), and is typically packaged under argon in amber glass or fluoropolymer‑lined containers to mitigate photolytic and oxidative degradation.
Kilogram‑scale production predominantly utilises the Vilsmeier‑Haack formylation of thiazole, employing phosphorus oxychloride (POCl₃) and dimethylformamide (DMF) in a jacketed glass‑lined reactor. The thiazole substrate (1.0 eq) is added to a pre‑formed Vilsmeier adduct maintained at –5 ± 2 °C to suppress the exothermic formation of tarry by‑products. The reaction mass is then warmed to 50–55 °C over 90 min and held for 6 h. Quenching into aqueous sodium acetate below 10 °C precipitates the aldehyde as a dark oil that is extracted into methyl tert‑butyl ether. The crude yield typically lies in the range 78–84 % after a single extraction; however, careful control of the POCl₃:DMF molar ratio at 1.05:1.00 suppresses the formation of dimeric 2,2'-(1,3-thiazole-2,5-diyl)bis(methylidene) species, which co‑distil and degrade the purity of later pharmaceutical batches. Batch records from a dedicated kilo‑lab facility indicate that when the agitation rate falls below 150 rpm in a 100 L reactor, localised overheating at the POCl₃ feed point elevates the dimeric impurity above 0.3 area‑%, rendering the material unsuitable for active pharmaceutical ingredient (API) synthesis without column chromatography.
Alternative oxidative routes—such as manganese dioxide (MnO₂) oxidation of 2‑(hydroxymethyl)thiazole—find application in academic settings but scale poorly due to the explosive potential of the MnO₂‑solvent slurry and the difficulty of removing sub‑micron manganese residues to < 2 ppm. Electrochemical oxidation in a divided flow‑cell employing a graphite anode and 0.1 M tetrabutylammonium tetrafluoroborate in acetonitrile has been reported to yield 89 % conversion at 20 mA·cm⁻², yet published data for multi‑kilogram campaigns are limited. The Vilsmeier‑Haack method, despite its handling hazards associated with POCl₃, remains the benchmark process because it can deliver ≥ 98.5 area‑% purity after fractional distillation (bp 74–76 °C at 1.33 kPa / 10 mmHg) without recourse to preparative chromatography.
Commercial specifications are stratified according to end‑use risk profiles. Distinguishing grades by their residual solvent fingerprints and controlled impurity thresholds defines the product’s fitness for early‑phase development versus late‑stage cGMP manufacture.
| Grade | Assay (wt%, NaOH titration) | HPLC Purity (area‑%, 254 nm) | Water (KF) | Residual DMF | Appearance | Typical Deployment |
|---|---|---|---|---|---|---|
| Technical (Stabilised) | ≥ 95.0 % | ≥ 95.5 % | ≤ 0.5 % | Not controlled | Amber liquid | Flavour candidate screening |
| Synthesis Grade | ≥ 97.0 % | ≥ 98.0 % | ≤ 0.3 % | < 500 ppm | Pale yellow, may crystallize | Bulk agrochemical intermediate |
| Pharmaceutical Intermediate | ≥ 99.0 % | ≥ 99.5 % | ≤ 0.1 % | < 100 ppm | Pale yellow crystals | API building block, ICH M7 control |
| Custom Sublimed | ≥ 99.8 % | ≥ 99.9 % | ≤ 0.05 % | < 10 ppm | White crystalline solid | Pre‑clinical imaging probe precursor |
All pharmaceutical‑intermediate material is qualified against ICH Q3C (residual solvents) and ICH Q3D (elemental impurities) with a permitted daily exposure for DMF limited to 8.8 mg·day⁻¹ (Class 2 solvent). The hydrochloride salt of the corresponding oxime is employed for potentiometric assay by alkaline hydroxylamine cleavage, giving end‑point precision of ± 0.2 % relative. Accelerated stability studies at 40 °C / 75 % RH over 6 months in hermetically sealed amber vials show a purity decrease of 0.8–1.2 area‑% for the synthesis grade but only 0.2 area‑% for the sublimed grade, attributable to the near‑absence of water and hydroquinone stabiliser that can catalyse oxidative ring‑opening.
Regioisomeric formyl-thiazoles exhibit markedly divergent behaviour in late‑stage C–H functionalisation sequences. Using conditions of Pd(OAc)₂ (5 mol%), pivalic acid (30 mol%), and K₂CO₃ in dimethylacetamide at 100 °C, the 2‑formyl isomer undergoes selective arylation at the 5‑position with aryl bromides furnishing 5‑aryl‑2‑thiazolecarboxaldehydes in isolated yields of 67–79 %. The 4‑carboxaldehyde counterpart provides a mixture of 2‑ and 5‑arylated products under identical conditions, often requiring chromatographic separation that reduces throughput in a 20 L Buchiglas autoclave to below economic viability for early‑phase medicinal chemistry. The selectivity is rationalised by the electron‑deficient nature of the 2‑formyl group, which directs the electrophilic palladium centre to the most electron‑rich C‑5 position, whereas the 4‑formyl group, being conjugated only through a single bond, offers a weaker polarisation. In addition, the 2‑aldehyde participates in imine‑directed C–H activation with N‑aryl imines, enabling further build‑up of conjugated pharmacophores, a transformation for which the 4‑isomer shows no productive conversion at 80 °C.
Kinetic profiling of a model Suzuki‑Miyaura cross‑coupling with 4‑tolylboronic acid using Pd(PPh₃)₄ (2 mol%) in THF/water at 60 °C revealed that 2‑thiazolecarboxaldehyde consumed in 18 min (kobs = 0.038 min⁻¹), while 4‑thiazolecarboxaldehyde required 45 min (kobs = 0.015 min⁻¹). The slower rate for the 4‑isomer is attributed to steric hindrance exerted by the adjacent sulfur atom, which shields the oxidative addition step when the formyl group is in the para‑like orientation. Process chemists translating these couplings to pilot scale (50 L Hastelloy reactor) therefore select the 2‑aldehyde whenever medium‑throughput library synthesis targets a C‑5 substituted thiazole scaffold, as the faster kinetics reduce cycle time and the risk of palladium black precipitation.
Industrial‑scale storage mandates inert gas blanketing with < 0.5 % oxygen in the container headspace and continuous refrigeration at 2–8 °C. The compound is hygroscopic and undergoes slow aerial oxidation to thiazole‑2‑carboxylic acid; a filled 200 L stainless‑steel drum with a polytetrafluoroethylene (PTFE) dip‑tube stored under 99.999 % nitrogen has been documented to accumulate 0.15 % carboxlic acid over 24 months, which still complies with the pharmaceutical‑intermediate specification. By contrast, a single exposure to ambient laboratory atmosphere (25 °C, 55 % RH) for 6 h during aliquot removal increased the acid content from 0.04 % to 0.22 %, underlining the necessity of closed‑loop transfer through nitrogen‑purged vacuum lines in cGMP facilities. Compatibility with common process solvents is generally high, but contact with primary and secondary amines must be rigorously avoided in storage because Schiff‑base formation occurs at room temperature within minutes; headspace gas‑chromatographic monitoring of a drum vented through a silica‑gel breather detected 12 ppm of N‑ethyl-1-(thiazol-2-yl)methanimine only 90 min after an operating error that allowed a trace ammonia atmosphere inside the containment glovebox.
The presence of a nitrogen atom in the heterocycle fundamentally alters the electrophilicity of the carbonyl carbon relative to furan‑ and thiophene‑based aldehydes. Hammett substituent constants through resonance (σR) derived from 13C NMR chemical shifts place 2‑thiazolyl as a stronger electron‑withdrawing group (σR ≈ 0.30) than 2‑thienyl (σR ≈ 0.22) and 2‑furyl (σR ≈ 0.17). Consequently, the rate of sodium bisulfite adduct formation in aqueous ethanol at pH 4.0 is approximately 3‑fold faster for 2-thiazolecarboxaldehyde compared to furfural, a property exploited in chemoselective purifications where the thiazole aldehyde is isolated from a mixture by bisulfite complexation while the furan aldehyde remains in the organic phase. However, the same electron deficiency retards acid‑catalysed acetalisation with ethylene glycol by a factor of 2.5, meaning that protective group strategies optimised for furan systems fail to reach completion (> 98 % conversion) unless the reaction temperature is raised from 80 °C to 110 °C in toluene with azeotropic water removal.
In multi‑component Hantzsch‑type thiazole syntheses, employing 2‑thiazolecarboxaldehyde as the aldehyde input results in a bis‑thiazole product distinct from that obtained with furfural. This is not merely a scaffold replacement; the C2‑aldehyde of the product inherits the nitrogen‑bearing ring, which alters the H‑bonding capacity of the final molecule and its interaction with biological targets such as the pyruvate:ferredoxin oxidoreductase (PFOR) complex. In vitro IC₅₀ measurements against PFOR from Giardia lamblia for a series of analogues demonstrated a 12‑fold improvement in potency when 2‑thiazolecarboxaldehyde was used over furfural in the same synthetic sequence, driving its adoption in second-generation 5‑nitrothiazole antiparasitics.
The aldehyde is a penultimate intermediate in the synthesis of nitazoxanide (FDA NDA 208698), a broad‑spectrum antiprotozoal thiazolide. As an electrophilic species, it triggers ICH M7 (Assessment and Control of DNA Reactive (Mutagenic) Impurities) concerns because structurally related aldehydes may act as in‑vivo alkylating agents. A staged threshold of toxicological concern (TTC) of 1.5 µg·day⁻¹ is applied to any residual 2‑thiazolecarboxaldehyde in the final drug substance, necessitating an LC‑MS/MS method with a limit of quantitation (LOQ) of 0.1 ppm (w/w). Pharmaceutical manufacturers routinely incorporate a polymer‑bound sulfonyl hydrazide scavenger (e.g., Biotage® PS‑TSH, loading 1.2 mmol·g⁻¹) in the work‑up train, bringing residual aldehyde from 800–1200 ppm after the coupling step down to < 1 ppm in the isolated product. Process validation batches at a contract manufacturing organisation using 30 kg input of the amine component showed that scavenging efficiency declined by 18 % when the scavenger resin was re‑used beyond 3 cycles, a finding incorporated into the master batch record to prevent out‑of‑specification results for mutagenic impurities.
| Property | 2-Thiazolecarboxaldehyde | 4-Thiazolecarboxaldehyde | 2-Furancarboxaldehyde (Furfural) | 2-Thiophenecarboxaldehyde |
|---|---|---|---|---|
| CAS | 10200-59-6 | 3364-80-5 | 98-01-1 | 98-03-3 |
| Boiling Point (°C, 10 mmHg) | 74–76 | 85–87 | 54–56 | 82–84 |
| Relative Rate of Bisulfite Adduct Formation (furfural = 1.0) | 3.1 | 2.0 | 1.0 | 1.3 |
| Regioselectivity in Pd‑Catalysed C–H Arylation | C5 > 95:5 | C2:C5 ≈ 1:1 | Not applicable (furan ring) | C5 > 90:10 |
| OSHA Hazard Classification | Combustible liquid, skin sensitiser | Irritant | Toxic (H301), corrosive | Harmful (H302) |
Extractable photostability data indicates that the neat chemical exposed to ICH Q1B Option 2 light conditions (overall illumination of 1.2 million lux·h, integrated UV of 200 W·h·m⁻²) generates 2.7 % of the corresponding carboxylic acid and a trace amorphization of the crystalline lattice, supporting the requirement for amber glass containers even during analytical handling.
