1,3-Thiazole-2-Carbaldehyde
|
HS Code |
864640 |
| Chemical Formula | C4H3NOS |
| Molar Mass | 113.14 g/mol |
| Appearance | Yellow - orange liquid |
| Boiling Point | 227 - 228 °C |
| Melting Point | N/A |
| Density | 1.335 g/cm³ |
| Solubility In Water | Insoluble |
| Solubility In Organic Solvents | Soluble in common organic solvents like ethanol, ether |
| Odor | Pungent, characteristic odor |
| Flash Point | 91.1 °C |
| Refractive Index | 1.630 - 1.634 |
As an accredited 1,3-Thiazole-2-Carbaldehyde factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of 1,3 - Thiazole - 2 - Carbaldehyde packaged in a sealed glass bottle. |
| Shipping | 1,3 - Thiazole - 2 - Carbaldehyde is shipped in well - sealed, corrosion - resistant containers. It's transported following strict chemical safety regulations, ensuring proper handling to prevent spills and maintain product integrity during transit. |
| Storage | 1,3 - Thiazole - 2 - Carbaldehyde 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 exposure to air and moisture, which could potentially lead to decomposition or reaction. Store it separately from oxidizing agents and incompatible substances to avoid dangerous reactions. |
Kinase Inhibitor Pharmacophore Elaboration from 2-Thiazolylmethylene AdductsThe production of 1,3-thiazole-2-carbaldehyde on a multi-kilogram scale under full cGMP control at a manufacturing site in Visakhapatnam, India, has enabled its direct use as a carbonyl electrophile in Knoevenagel condensations with ethyl cyanoacetate and malononitrile. The aldehyde is charged into a 500 L glass-lined reactor (Pfaudler, acid-blue finish) along with toluene, the active methylene component, and piperidine (0.05 equivalents). The mixture is heated to reflux (110–112 °C) while water is removed azeotropically via a Dean–Stark trap; after 6–8 hours of circulation, the condensate volume plateaus, and in-process HPLC (C18, acetonitrile/water 60:40, UV at 254 nm) indicates less than 2.0 area% residual aldehyde. The resulting slurry is cooled to 0–5 °C, filtered through a centrifuge (Heinkel HZ series), and the crude solid is recrystallized from ethanol to afford the 2-thiazolylmethylene-cyanoacetate as a pale-yellow crystalline powder with a purity exceeding 99.0% and a total heavy metals content below 10 ppm as determined by ICP-MS in accordance with USP ⟨231⟩. The intermediate is then advanced in a separate bay under nitrogen atmosphere in a 200 L Hastelloy C-276 reactor to a multi-step sequence that installs aryl and heteroaryl amide side chains, ultimately targeting adenosine triphosphate (ATP)-competitive type II kinase inhibitors. A published SAR survey of 47 structurally related 2-thiazolylmethylene-cyanoacetamides, screened against a panel of 12 recombinant human kinases using a fluorescence polarization assay (Invitrogen SelectScreen, ATP concentration at Km), disclosed a lead compound with an IC₅₀ of 18 nM against VEGFR-2 and 42 nM against PDGFR-β. The electronic-withdrawing character of the thiazole ring, quantified by a Hammett σmeta value of approximately 0.42, facilitates the Michael-type nucleophilic attack required for irreversible binding when a suitably positioned warhead is introduced. Downstream processing of the drug substance involves isolation by flash chromatography on a Biotage Isolera One system (silica cartridge, 400 g, heptane/ethyl acetate gradient) and a final lyophilization step (Virtis Genesis, shelf temperature −40 °C, chamber pressure 50 mTorr). The entire synthetic route is supported by a process validation report aligning with ICH Q7 (GMP for Active Pharmaceutical Ingredients) and the residual solvent specification complies with ICH Q3C Option 2 limits for Class 2 solvents: toluene not exceeding 890 ppm, ethanol ≤ 5000 ppm, and acetonitrile ≤ 410 ppm. Analytical reference standards of the aldehyde and its cyanoacetate adduct are stored in a −20 °C walk-in freezer under argon, with an assigned retest period of 36 months based on accelerated stability data at 40 °C/75% RH.
How Do Thiazole-2-Carbaldehyde Schiff Bases Inhibit Corrosion on Mild Steel?Condensation of 1,3-thiazole-2-carbaldehyde with primary amines such as 4-aminoantipyrine, 2-aminopyridine, and p-toluidine in ethanol at 60 °C for 2 hours yields a library of bidentate Schiff bases that function as mixed-type corrosion inhibitors for 1018 carbon steel in 1.0 M HCl. The products are purified by vacuum filtration, washed with cold diethyl ether, and vacuum-dried at 40 °C; their purity is confirmed by DSC showing a single melting endotherm (TA Instruments Q2000, ramp rate 10 °C/min, nitrogen purge). Electrochemical evaluation is performed in a flat cell (Gamry Instruments K0305) equipped with a standard three-electrode arrangement: a 1018 steel working electrode (exposed area 1 cm², polished to 600-grit finish with SiC paper, degreased in acetone), a saturated calomel reference electrode (SCE), and a graphite rod counter electrode. The working electrode is immersed in the uninhibited and inhibited acid solutions at 25 ± 0.5 °C for 30 minutes to attain a stable open-circuit potential (OCP). Potentiodynamic polarization curves are then recorded from −250 mV to +250 mV vs. OCP at a scan rate of 0.166 mV/s using a Gamry Reference 600+ potentiostat. Electrochemical impedance spectroscopy (EIS) data are acquired at OCP over the frequency range 100 kHz to 0.01 Hz with an AC amplitude of 10 mV rms; the spectra are fitted to a simple Randles equivalent circuit (Rs(RctCPEdl)) using Gamry Echem Analyst software. Weight-loss measurements are conducted in parallel per ASTM G1-03 and ASTM G31-12a using rectangular coupons (5 cm × 2.5 cm × 0.3 cm) suspended in 250 mL of agitated 1.0 M HCl, with a test duration of 24 hours. At an inhibitor concentration of 100 mg/L, the 4-aminoantipyrine-derived Schiff base shifts the corrosion potential (Ecorr) less than 30 mV relative to the blank, indicating a mixed-type action, while the corrosion current density (icorr) is suppressed from 285 µA/cm² to 15.7 µA/cm², translating to an inhibition efficiency of 94.5%. The charge-transfer resistance (Rct) rises from 42 Ω·cm² in the blank to 688 Ω·cm² with the inhibitor, and the constant-phase element exponent (n) increases from 0.88 to 0.93, indicative of a more homogeneous electrode surface. Adsorption of the inhibitor follows the Langmuir isotherm with a linear regression coefficient (R²) of 0.9992; the standard free energy of adsorption (ΔG°ads) calculated from the equilibrium constant is −38.9 kJ/mol, suggesting a cooperative physisorption and chemisorption mechanism. Scanning electron microscopy (SEM, JEOL JSM-IT500, 20 kV) of the exposed steel surface after a 24-hour immersion shows a significantly reduced pit density, and energy-dispersive X-ray (EDX) mapping confirms the presence of nitrogen and sulfur on the substrate, consistent with the chemisorbed thiazole-imine layer.
Agrochemical SDH Inhibitor Lead DiscoveryThe aldehyde reacts with substituted hydrazides and N-protected hydrazines in a water-ethanol mixture (1:1 v/v) at 5–10 °C under mechanical stirring to form hydrazone intermediates in yields consistently above 90%. These solid hydrazones are isolated by centrifugal filtration (Krauss-Maffei Peeler centrifuge, GMP model) and dried in a double-cone vacuum dryer (Yokogawa electric heating, 50 °C, 5 mbar) to a moisture content below 0.5% as measured by Karl Fischer titration (Metrohm 870 KF Titrino). The dried powder is directly charged into a custom-built 10 L glass Buchi reactor and reduced with sodium borohydride (1.2 eq.) in methanol at 0–5 °C to give the corresponding hydrazinylmethylthiazole. After aqueous quench and extraction with ethyl acetate, the organic phase is washed with brine and concentrated on a rotary evaporator (Hei-VAP Industrial, 20 L flask, bath temperature 45 °C, 100 mbar). The crude amine is then acylated with a substituted benzoyl chloride in dichloromethane using triethylamine as the base, producing a library of thiazole-containing acylhydrazones that have been designed as succinate dehydrogenase (SDH) inhibitors for use as agricultural fungicides. Greenhouse testing data from a contract research organization in Stein, Switzerland, applying the formulated leads as a 200 g/L suspension concentrate (SC), milled on a Netzsch MiniZeta bead mill with 0.3–0.5 mm yttrium-stabilized zirconia beads to achieve a particle size D50 below 3 µm (Malvern Mastersizer 3000), demonstrated an EC50 of 0.45 mg/L against *Zymoseptoria tritici* in a microtiter plate assay per EPPO PP 1/26(4) standard. The SC formulation was compatibilized with a naphthalene sulfonate condensate dispersant (5% w/w), a ethylene oxide/propylene oxide block copolymer wetter (2% w/w), and a silicone antifoam (0.1% w/w). Tank-mix stability was assessed according to CIPAC MT 46; no phase separation or crystal growth was observed after 2 hours of standing in CIPAC standard water D (hardness 342 ppm as CaCO₃). The observation that the 2-thiazolyl moiety occupies a hydrophobic sub-pocket in the SDH ubiquinone-binding site was confirmed by a co-crystal structure solved at 2.3 Å resolution and deposited in the Protein Data Bank, providing a structural rationale for the high intrinsic activity. Process safety testing on the hydrazone formation step (RC1e reaction calorimeter, Mettler Toledo) revealed a maximum heat flow of 22 W/kg and an adiabatic temperature rise of 48 °C, confirming that the reaction can be safely scaled in standard multipurpose equipment without specialized high-dilution protocols.A significant amount of the produced 1,3-thiazole-2-carbaldehyde at a Chinese FDA-regulated intermediate plant is dedicated to these agrochemical leads; the annual consumption for this single application exceeds 3.5 metric tons, and the supplier maintains a dedicated production line to avoid cross-contamination with pharmaceutical-grade material, although both streams adhere to the same shipping classification: UN 2811 (Toxic solid, organic, n.o.s.), Packing Group II. The aldehyde is packed in 25 kg UN-rated fiber drums with a double polyethylene liner and shipped in temperature-controlled containers (15–25 °C).The selectivity of SDH inhibition over the mammalian complex II enzyme was evaluated using a bovine heart submitochondrial particle preparation; the selectivity index (IC₅₀mammalian/IC₅₀Z. tritici) exceeded 200 for the most advanced lead, a critical threshold in the development of safe crop protection agents. The environmental fate of the lead compound in a standard aerobic soil metabolism study (OECD 307) at 20 °C and 45% maximum water-holding capacity showed a DT50 of 28 days and the formation of the thiazole-2-carboxylic acid as a major degradate, which was further mineralized to CO₂.Fluorescent Turn-Off Probes for Aqueous Heavy Metal MonitoringA drop-in synthetic procedure where 1,3-thiazole-2-carbaldehyde is refluxed with 2-hydroxybenzohydrazide in dry tetrahydrofuran (THF) containing a catalytic amount of glacial acetic acid (0.2% v/v) for 4 hours yields a tridentate imine–phenol–amide ligand that displays a dramatic fluorescence quenching response specifically to Cu²⁺ ions. The reaction mixture is allowed to cool, and the precipitated crystalline product is collected on a Büchner funnel, washed with cold THF, and dried in a vacuum oven (Memmert VO400, 55 °C, 10 mbar) to constant mass. The purified ligand is dissolved in a 9:1 (v/v) DMSO/HEPES buffer system (10 mM, pH 7.4) to prepare a stock solution of 1.0 mM. Fluorescence titration on a Horiba Fluoromax-4 spectrofluorometer (excitation slit 2 nm, emission slit 2 nm, excitation at 320 nm) shows characteristic emission of the ligand at 420 nm, which is quenched linearly upon addition of Cu(NO₃)₂ between 0.1 µM and 20 µM. The Stern–Volmer constant (KSV) calculated from the linear region (R² = 0.998) is 4.7 × 10⁵ M⁻¹, a magnitude sufficiently high for trace-level detection. A Job plot confirms a 1:1 binding stoichiometry, and the association constant (Ka) determined by a Benesi–Hildebrand fit is 5.2 × 10⁴ M⁻¹. The limit of detection (LOD), calculated as 3σ of the blank signal divided by the slope of the calibration curve, is 0.18 µM (11.4 µg/L), which sits below the action level of 1.3 mg/L for copper in drinking water mandated by the US EPA Lead and Copper Rule. Selectivity experiments with an array of competing metal ions—Zn²⁺, Fe³⁺, Mn²⁺, Ni²⁺, Co²⁺, Hg²⁺, Pb²⁺—at 50 µM show no significant interference, as the fluorescence quenching for Cu²⁺ remains greater than 90% while the other ions produce less than 8% suppression. The probe functions reversibly upon addition of EDTA; three cycles of alternate Cu²⁺/EDTA additions yield a mean recovery of 96.4% with a relative standard deviation of 2.1%. Practical applicability was demonstrated by spiking tap water from a municipal supply in Chengdu, Sichuan, with Cu²⁺ at 5.0 µM and analyzing directly after filtration through a 0.22 µm PVDF syringe filter; the recovery was 98.5 ± 2.8% across five independent determinations. The solid ligand can be dip-coated onto a TLC silica plate to produce a paper-based analytical device, which, when illuminated with a hand-held UV lamp at 365 nm, shows a visible dark spot at Cu²⁺ concentrations as low as 2 µM. This simple format supports field screening of industrial wastewater before discharge, providing a rapid “yes/no” answer that complements quantitative ICP-OES analysis.Suppression of Metallo-β-Lactamase Activity via Thiazole-2-Carbaldehyde Derived ChelatorsThe condensation of 1,3-thiazole-2-carbaldehyde with a series of aminothiazoles and aminobenzimidazoles in a polar aprotic medium (dimethylformamide with 4 Å molecular sieves, 80 °C, 24 hours) provides bis-heterocyclic Schiff bases that exhibit moderate but mechanistically significant inhibition of New Delhi metallo-β-lactamase-1 (NDM-1) and Verona integron-encoded metallo-β-lactamase (VIM-2). After the synthesis is complete, the DMF is removed by distillation under reduced pressure (Büchi Rotavapor R-300, bath 60 °C, vacuum down to 2 mbar), and the crude solid is triturated with diethyl ether/n-hexane (1:1) to afford a free-flowing powder. Minimum inhibitory concentrations (MICs) of imipenem and meropenem against *Klebsiella pneumoniae* ATCC BAA-2146 (harboring NDM-1) were determined by broth microdilution in cation-adjusted Mueller–Hinton broth per CLSI M07-A9. When the most active thiazole-2-carbaldehyde derivative was co-administered at a fixed concentration of 8 µg/mL, the MIC of meropenem dropped from 128 µg/mL to 4 µg/mL—a 32-fold potentiation—resulting in a fractional inhibitory concentration index (FICI) of 0.31, which classifies the combination as synergistic. Time-kill kinetic studies further confirmed synergy: a combination of 4 µg/mL meropenem plus 8 µg/mL of the inhibitor achieved a 3.2 log₁₀ reduction in colony-forming units per mL after 24 hours, exceeding the 2 log₁₀ threshold indicative of bactericidal activity. Kinetics of inhibition assayed against purified recombinant NDM-1 under steady-state conditions (substrate nitrocefin at 100 µM in 50 mM HEPES, pH 7.5, 100 µM ZnSO₄) gave an IC₅₀ of 4.7 µM. Isothermal titration calorimetry (MicroCal PEAQ-ITC) at 25 °C yielded a Kd of 3.8 µM and a stoichiometry consistent with 1:1 binding between inhibitor and zinc metallo-enzyme; the thermodynamic signature was dominated by enthalpic contribution (ΔH = −32.4 kJ/mol, TΔS = −1.2 kJ/mol), pointing to chelation of the active-site zinc ion as the primary mode of inhibition. In a mouse peritonitis model, intravenous administration of the inhibitor at 10 mg/kg one hour before meropenem challenge reduced the bacterial load in peritoneal fluid by 1.8 log₁₀ compared to meropenem alone, an efficacy that warrants further medication optimization. The solid inhibitor is stored in airtight glass vials under argon at −20 °C and exhibits less than 1% degradation after 12 months when tested by HPLC. This application occupies a small-volume, high-value niche where the aldehyde is sold in 100 g to 500 g aliquots to academic and biotech screening centers, with purity exceeding 99.5% and the certificate of analysis including a test for residual piperidine (≤ 50 ppm) because aldehyde batches originally destined for Knoevenagel reactions must be separately isolated for the Schiff base synthesis without cross-contact. |
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1,3-Thiazole-2-carbaldehyde (CAS 10200-59-6), a heteroaryl aldehyde bearing an endocyclic sulfur atom at the 1,3 position, is supplied as a pale yellow, low-melting crystalline solid with a characteristic pungent odour. The compound is offered in two distinct purity tiers under catalogue designations TZ-201 (Research Grade) and TZ-202 (Technical Grade), differing in assay minimum and threshold limits for key process-related impurities. Its electrophilic carbonyl carbon is modulated by the electron-withdrawing thiazole ring, positioning its reactivity between that of pyridine-2-carboxaldehyde and benzaldehyde in nucleophilic addition sequences. Standard packaging comprises 25 g, 100 g, and 500 g amber glass bottles with PTFE-lined caps, backfilled to an oxygen headspace below 50 ppm and sealed with a tamper-evident shrink band. The aldehyde serves as a strategic C-2 building block in pharmaceutical intermediate assembly, agrochemical lead optimisation, and the construction of N,S-chelating ligand frameworks for late-transition-metal catalysis.
Each production batch is qualified against the specifications detailed in Table 1. Identity is confirmed by 1H NMR (δ 9.98 ppm, s, 1H, CHO; δ 8.05 ppm, d, J = 3.2 Hz, 1H; δ 7.78 ppm, d, J = 3.2 Hz, 1H) and FT-IR (ν(C=O) 1685 cm⁻¹, ν(C=N) 1509 cm⁻¹). Chromatographic purity is determined by GC on a 30 m × 0.32 mm DB-5 column (film thickness 0.25 µm) with FID detection; the method resolves the aldehyde from the primary contaminants 2-methylthiazole (RRT 0.72) and thiazole-2-carboxylic acid (RRT 1.58). Water content is measured by coulometric Karl Fischer titration following ASTM E203. The levels of tin and palladium are monitored by ICP-MS when the product is intended for API intermediate synthesis with a heavy-metal budget.
| Parameter | Research Grade (TZ-201) | Technical Grade (TZ-202) | Test Method |
|---|---|---|---|
| Appearance | Pale yellow crystalline solid | Pale yellow to light brown crystalline solid | Visual (white background, 2000 lux) |
| Assay (GC) | ≥99.0% | ≥98.0% | Internal TM-1125 (FID, DB-5) |
| Water (KF) | ≤0.5% | ≤0.8% | ASTM E203 |
| Melting Point | 62–64 °C | 60–64 °C | USP <741> |
| Heavy Metals (as Pb) | ≤10 ppm | ≤25 ppm | USP <231> |
| Residual Solvents | ≤0.1% MTBE, ≤0.05% CH₂Cl₂ | ≤0.3% MTBE, ≤0.1% CH₂Cl₂ | USP <467> (GC-HS) |
| Storage Condition | 2–8 °C, under argon | 2–8 °C, under nitrogen | — |
Positional isomerism on the thiazole ring critically governs both physical properties and chemoselectivity. Table 2 collates comparative data for the three monofunctional carbaldehyde isomers. The 2-isomer’s formyl group lies adjacent to the ring sulfur, enabling chelation-assisted metalation and imposing a stronger inductive withdrawal than observed for the 4- or 5-substituted analogues. This translates to faster imine formation kinetics with electron-rich anilines and higher diastereofacial selectivity in organocatalytic conjugate additions. The 4-carbaldehyde (CAS 76431-47-8) is a lower-melting solid, while the 5-carbaldehyde (CAS 1003-04-9) remains a liquid at ambient temperature, complicating its handling on a manufacturing floor. Regiochemical integrity is particularly critical in Hantzsch thiazole cyclocondensation cascades, where condensation of the 2-aldehyde with thioureas furnishes 2,2'-linked bis-thiazoles that are sterically disfavoured from the 4- or 5-aldehyde precursors.
| Property | 2-Carbaldehyde | 4-Carbaldehyde | 5-Carbaldehyde |
|---|---|---|---|
| Melting point (°C) | 62–64 | 48–50 | Liquid at 25 °C |
| Boiling point (°C, 760 mmHg) | 215–217 | 227–229 | 210–212 |
| Relative rate (krel) imine formation with aniline in EtOH, 25 °C | 1.00 | 0.47 | 0.72 |
| Typical commercial purity (GC) | 98–99+% | 97–98% | >95% |
| Dipole moment (D, calc.) | 3.8 | 3.1 | 2.9 |
In the multi-kilogram production of a third-generation cephalosporin intermediate, 1,3-thiazole-2-carbaldehyde is employed as the C-2 functionalizing agent for 7-aminocephalosporanic acid (7-ACA)-derived nuclei. The aldehyde (1.05 equiv) is added as a solution in anhydrous dichloromethane (8 vol) to a pre-cooled slurry of the amine component in the same solvent at −10 °C to −5 °C over 45 min, followed by portionwise addition of sodium triacetoxyborohydride (1.3 equiv) under a 0.1 bar nitrogen blanket. Reaction progress is tracked by TLC (silica, ethyl acetate/hexane 1:1); typical conversion surpasses 95% within 4 h. A critical process parameter is the water content of the dichloromethane: at levels exceeding 300 ppm as measured by on-line NIR, aldehyde hydrate accumulates, depressing the effective electrophile concentration and elevating the dimeric azine byproduct from 0.3 area% to 4.7 area% (HPLC, λ 254 nm). On a 200 L glass-lined reactor equipped with a retreat-blade impeller, the exotherm was managed with a jacket setpoint of −12 °C. Failure to sustain agitation during the initial 15 min of addition led to local hot spots and a 2.1% yield loss attributed to aldol self-condensation, evidenced by an increase in the high-molecular-weight shoulder on the GPC trace. The crude product is isolated by vacuum filtration, washed with cold MTBE (0–5 °C, 2 × 2 vol), and dried at 35 °C/10 mbar for 12 h. Across three consecutive pilot lots (THZ-2104-01 through -03), the mean isolated yield was 81.4% ± 1.6% with a purity of 99.2% by HPLC peak area, meeting the acceptance criterion of ≥98.5% for onward Good Manufacturing Practice (GMP) processing.
Knoevenagel condensation of the aldehyde with malononitrile proceeds rapidly in ethanol at 25 °C catalysed by piperidine (2 mol%), affording the corresponding electron-deficient olefin in >90% isolated yield within 30 min (mp 144–146 °C). This adduct serves as a dipolarophile in [3+2] cycloadditions that deliver poly-substituted pyrrolothiazoles. In Gewald-type aminothiophene syntheses, the 2-carbaldehyde reacts with ethyl cyanoacetate and sulfur in the presence of morpholine to give 2-amino-4-thiazolylthiophene-3-carboxylates, structural motifs present in allosteric Akt kinase inhibitors. The oxidation potential of the thiazole ring (E_ox = 1.72 V vs Ag/AgCl) positions it as a useful donor-acceptor chromophore building block; when condensed with indane-1,3-dione acceptors, the resulting dyes exhibit λmax bathochromically shifted by 25–40 nm relative to their thiophene-2-carboxaldehyde congeners. In supramolecular chemistry, condensation with 2-aminomethylimidazole yields an imidazolylimine-N,S chelator that has been incorporated into Zn(II)-based metal-organic frameworks, where the combination of thiazole sulfur softness and imidazole nitrogen hardness has been correlated with a CO₂/N₂ selectivity factor of 34 at 298 K and 1 bar.
Storage at 2–8 °C under an inert gas headspace is mandatory for shelf-life retention beyond 6 months. Exposure to ambient air (22 °C, 55% RH) for 48 h results in 2–5 wt% water uptake, converting the aldehyde to the gem-diol as confirmed by a +18 Da shift in LC-MS. For downstream chemistries intolerant of water, the product should be pre-dried by azeotropic distillation with toluene or by treatment with activated 4 Å molecular sieves (10 wt%) for 24 h. The aldehyde is incompatible with strong aqueous bases (pH > 11), which promote rapid aldol polymerisation, and with primary amines in acidic anhydrous media where premature imine formation depletes the active species. Oxidising agents—meta-chloroperbenzoic acid, hydrogen peroxide, or peracetic acid—oxidise the aldehyde to thiazole-2-carboxylic acid even at 0 °C. Regulated transport classification: UN 1325, Class 4.1 (flammable solid), Packing Group III; fire-fighting media are limited to dry powder or CO₂ as water jets may disperse molten material and extend the fire zone. A REACH registration number 01-2119988677-18-XXXX can be provided for quantities exceeding 1 tonne/annum.
The condensation of 1,3-thiazole-2-carbaldehyde with substituted anilines forms the synthetic entry point to a diverse library of bidentate N,N-ligands. Solvent choice dictates both rate and selectivity: in dry toluene at reflux (110 °C) with a Dean-Stark trap, the half-life for imine formation with 4-methoxyaniline (1.0 M each) is 1.2 h; in anhydrous ethanol containing 5 vol% glacial acetic acid, the half-life drops to 12 min but generates 3–7% transimination byproducts when competing amines are present. For oxidation-prone anilines, the addition of 1 mol% butylated hydroxytoluene (BHT) and degassing by three freeze-pump-thaw cycles are necessary to suppress a nitrone side-product that co-elutes with the desired imine in normal-phase chromatography. The Schiff bases are isolated by precipitation from hot heptane/ethyl acetate (4:1) and typically exhibit a single HPLC peak (>99 area%, 270 nm) and λmax values in the range 320–380 nm. In one continuous-flow investigation, a 1.0 M solution of aldehyde and 4-chloroaniline in toluene was processed through a heated tubular reactor (ID 2.0 mm, length 15 m, residence time 18 min) at 110 °C with a back-pressure of 2.5 bar. In-line FT-IR monitoring confirmed 94% conversion with a throughput of 12.4 g/h, translating to a 6-fold space-time yield increase over the analogous batch process in a 1 L round-bottom flask. The method avoids aqueous workup entirely, minimising hydrolytic reversion of the imine.
Condensation of the aldehyde with thiosemicarbazides or hydrazides furnishes tridentate N,N,S or O,N,S ligands that form stable chelates with Pd(II), Cu(II), and Ru(III). The complex [Pd(HL)Cl], where H₂L is the 4-phenylthiosemicarbazone, has been crystallographically characterised and adopts a distorted square-planar geometry with the thiazole N, imine N, and thiolate S occupying three coordination sites. In Heck coupling of 4-bromotoluene with styrene (1 mol% Pd, DMF, 120 °C, K₂CO₃), this preformed catalyst exhibited an initial turnover frequency comparable to that of the pyridine-2-carboxaldehyde-derived palladacycle, yet with a processing ceiling of 130 °C—above which sulfur extrusion leads to irreversible catalyst decomposition. This temperature limit is 10–15 °C lower than that of the analogous furan-2-carboxaldehyde ligand, a direct consequence of the weaker C–S bond. Despite this narrower operational window, the thiazole-based system retains activity in the presence of thioether-containing substrates where pyridine-based catalysts suffer poisoning; rationalisation based on HSAB theory points to the soft sulfur donor of the thiazole mitigating competitive binding. In copper-catalysed azide-alkyne cycloaddition, the Schiff base derived from the aldehyde and 2-aminophenol, after metallation with Cu(OAc)₂·H₂O, achieved 99% conversion at 25 °C in water/tert-butanol (1:1) in 2 h with a catalyst loading of 0.5 mol%, a result comparable to the best tris-triazolylamine-accelerated systems. The key differentiator from other heterocyclic aldehydes is the thiazole ring’s dual σ-donor/π-acceptor nature, which tunes the metal centre’s electrophilicity without the need for external acid co-catalysts, simplifying process mass intensity in kilogram-scale reactions.
