2-(3-Formyl-4-Hydroxyphenyl)-4-Methyl-5-Thiazolecarboxylic Acid Ethyl Ester

Product Name 2-(3-Formyl-4-Hydroxyphenyl)-4-Methyl-5-Thiazolecarboxylic Acid Ethyl Ester
Alias FC-11
Einecs 681-427-8
Mininmum Order 1mg
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, 2-(3-Formyl-4-Hydroxyphenyl)-4-Methyl-5-Thiazolecarboxylic Acid Ethyl Ester is supplied with ≥98% purity (HPLC) and a certified melting point range, making it suitable for use as a pharmaceutical impurity reference standard.

Specifications

HS Code	484026
Chemical Formula	C14H13NO5S
Molecular Weight	307.32
Appearance	Solid (usually)
Solubility In Water	Low solubility in water, likely hydrophobic
Solubility In Organic Solvents	Soluble in some organic solvents like ethanol, dichloromethane
Melting Point	Specific value would require experimental determination
Boiling Point	Difficult to estimate precisely without data, but higher than common low - boiling compounds
Density	Estimated density would be in the range typical for organic compounds
Stability	Stable under normal conditions if stored properly away from strong oxidants and extreme temperatures

As an accredited 2-(3-Formyl-4-Hydroxyphenyl)-4-Methyl-5-Thiazolecarboxylic Acid Ethyl Ester factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

Packing & Storage

Packing	100g of 2-(3 - Formyl-4 - Hydroxyphenyl)-4 - Methyl-5 - Thiazolecarboxylic Acid Ethyl Ester in sealed container.
Shipping	The chemical 2-(3 - Formyl - 4 - Hydroxyphenyl)-4 - Methyl - 5 - Thiazolecarboxylic Acid Ethyl Ester will be shipped in properly sealed, corrosion - resistant containers. Shipment will follow strict chemical transportation regulations to ensure safety during transit.
Storage	Store “2-(3 - Formyl - 4 - Hydroxyphenyl)-4 - Methyl - 5 - Thiazolecarboxylic Acid Ethyl Ester” in a cool, dry place away from direct sunlight. Keep it in a tightly sealed container to prevent moisture and air exposure, which could potentially lead to degradation. Avoid storing near sources of heat or flammable materials.

Application of 2-(3-Formyl-4-Hydroxyphenyl)-4-Methyl-5-Thiazolecarboxylic Acid Ethyl Ester

What Makes the 3‑Formyl‑4‑Hydroxy Moiety Critical for Xanthine Oxidase Inhibition?

In the commercial synthesis of febuxostat, a non‑purine xanthine oxidase inhibitor monographed in USP and EP, the ethyl ester of 2‑(3‑formyl‑4‑hydroxyphenyl)‑4‑methyl‑5‑thiazolecarboxylic acid operates as the immediate precursor to the nitrile function. The formyl group is condensed with hydroxylamine hydrochloride at a molar ratio of aldehyde to NH₂OH·HCl of 1 : 1.05 in aqueous methanol at 50 – 60 °C while maintaining pH 4.0 – 4.5 with sodium acetate. Deviation of pH above 5.0 triggers a Cannizzaro side reaction that converts the formyl substituent into a mixture of carboxylate and hydroxymethyl impurities, reducing forward yield by 8 – 12 %. The resulting oxime intermediate is isolated via centrifugation in a gasket‑sealed bag centrifuge lined with polypropylene felt, then dried under vacuum at 45 °C for 12 h to a loss‑on‑drying below 0.5 %.

Dehydration of the oxime to the corresponding cyano intermediate determines the overall purity profile of the active pharmaceutical ingredient. A comparison of three dehydration protocols scaled to 2000 L glass‑lined reactors equipped with 3‑blade retreat‑curve impellers running at 75 rpm is set out in the table below. Acetic anhydride in the presence of potassium carbonate achieves the narrowest impurity envelope, limiting the des‑formyl degradation product to ≤ 0.10 % by HPLC area at 230 nm. The crude nitrile is recrystallized from isopropanol/water (7 : 3 v/v) with hot filtration through a 0.45 µm PTFE membrane cartridge to yield febuxostat meeting USP <621> chromatographic purity and ICH Q3C residual solvent thresholds for Class 3 solvents (isopropanol ≤ 5000 ppm, methanol ≤ 3000 ppm). Batch records indicate that the aldehyde intermediate must be stored under 99.95 % nitrogen blanket with ≤ 10 ppm dissolved oxygen, as autoxidation to the 3‑carboxy‑4‑hydroxy analogue proceeds at a rate of 0.02 % h⁻¹ at 25 °C in the presence of ambient light, compromising final API potency.

Dehydrating Agent	Molar Equiv.	Temperature (°C)	Time (h)	Yield of Nitrile (%)	HPLC Purity (%)
Acetic anhydride / K₂CO₃	2.0	60 – 65	4	88 – 92	≥ 99.5
Trifluoroacetic anhydride	1.2	20 – 25	2	78 – 84	98.3 – 99.0
Phosphorus oxychloride	1.5	45 – 50	6	65 – 70	95.1 – 97.8

Coordination‑Induced Fluorescence Turn‑On via Hydrazone Formation

Upon reaction with hydrazine in DMSO/HEPES buffer (1 : 9 v/v, pH 7.4) the aldehyde group of the thiazole ester generates a conjugated hydrazone that locks the molecule into a planar geometry, blocking non‑radiative decay and yielding a 160‑fold fluorescence enhancement at 478 nm. A probe loading of 10 µmol L⁻¹ provides a linear response range of 0.005 – 2.0 mg L⁻¹ hydrazine with a calculated limit of detection of 3.2 µg L⁻¹ (based on 3σ/slope, ICH Q2(R1) validation protocol). The phenolic hydroxyl participates in an excited‑state intramolecular proton transfer (ESIPT) relay that is disrupted by chelation of Al³⁺ or Zn²⁺, producing a ratiometric dual‑emission output with isoemissive points at 412 nm and 532 nm. For industrial hygiene monitoring, strips of Whatman Grade 1 chromatography paper are dip‑coated in a 1.0 wt% probe solution in ethyl acetate containing 0.5 wt% poly(methyl methacrylate) as binder, then dried at 60 °C for 90 s in a forced‑air tunnel. When exposed to hydrazine vapour at 0.1 – 10 ppm, the strips exhibit a colour shift from pale yellow to intense green under 365 nm UV illumination, quantifiable with a handheld fluorometer calibrated against EPA SW‑846 Method 8321B.

Compliance validation for use in wastewater alert systems adheres to ISO 15839:2003 for on‑line water quality sensors. A critical operational boundary is the presence of ammonia at concentrations above 500 mg L⁻¹, which forms a competing imine and reduces turn‑on efficiency by 40 %. Probe solubility below pH 5 drops sharply, necessitating formulation with 10 % cyclodextrin inclusion complex to maintain colloidal stability during field deployment.

In continuous twin‑screw compounding of polypropylene impact copolymer masterbatches, the title compound is metered into the feed throat of a Coperion ZSK 26 Mc¹⁸ co‑rotating extruder with L/D 44 and atmospheric vent at barrel zone 6. The aldehyde group undergoes thermal grafting onto maleic anhydride‑functionalized PP backbone residues, while the hindered phenolic hydroxyl donates hydrogen atoms to peroxy radicals during long‑term thermal ageing. Masterbatch let‑down ratios of 5 – 8 wt% correspond to a net concentration of 0.2 – 0.8 wt% active species in the final injection‑moulded part. Processing is confined to a melt temperature window of 190 – 220 °C; excursions above 225 °C initiate retro‑aldehyde oxidation that consumes the grafting anchor and leaves unbound low‑molecular‑weight fragments, causing die‑lip deposit accumulation measurable as > 50 mg m⁻² per 8‑h run. Finished automotive interior trims retain ≥ 70 % of original elongation at break after 2000 h in a forced‑air oven at 150 °C (ISO 188:2011) and exhibit oxidative induction time exceeding 45 min at 190 °C under ASTM D3895‑19 compared to 8 min for the unstabilized control.

Migration kinetics into food simulants are tested per EU 10/2011 annex V: the specific migration limit for the ester‑hydrolysed acid is 0.05 mg kg⁻¹ when tested with 3 % acetic acid at 70 °C for 2 h. The antioxidant is incompatible with co‑addition of primary amine‑based hindered amine light stabilizers (HALS) because Schiff base formation at the polymer‑melt interface reduces the effective radical‑trapping stoichiometry by 1.4 mol per mol of amine, as determined by ESR spin‑trapping experiments with POBN. Pre‑drying of the compound at 40 °C under –0.095 MPa for 4 h is mandatory when ambient relative humidity exceeds 60 %, as residual moisture leads to foaming and aldehyde hydrolysis during extrusion, lowering bulk density to 0.42 g cm⁻³ versus the specified 0.68 g cm⁻³.

When the Thiazole Ester Hydrolyzes to the Acid for Amide Coupling

Controlled alkaline hydrolysis in 2.5 N NaOH at a molar ratio of ester to hydroxide of 1 : 2.5 in 95 % ethanol under reflux (78 °C, 6 h) converts the ethyl ester quantitatively to 2‑(3‑formyl‑4‑hydroxyphenyl)‑4‑methylthiazole‑5‑carboxylic acid. After vacuum distillation of ethanol and acidification to pH 1.5 with 6 N HCl at 5 – 10 °C, the free acid is filtered and washed until chloride content is ≤ 50 ppm by Mohr titration. The acid is activated with EDC·HCl (1.2 equiv) and HOBt (1.0 equiv) in anhydrous DMF at 0 °C, then coupled with substituted anilines containing electron‑withdrawing groups to yield a library of thiazole‑4‑carboxamides. A typical coupling with 2‑bromo‑4‑(trifluoromethyl)aniline delivers the corresponding amide in 82 – 87 % yield after silica‑gel chromatography (eluent hexane/ethyl acetate 3 : 1), with HPLC purity ≥ 97.5 % at 254 nm.

These amides enter glasshouse screening for inhibition of Rhizoctonia solani and Botrytis cinerea according to OECD 509 and EPPO PP 1/26(4) guidelines. Lead candidates exhibit EC₅₀ values below 2.5 mg L⁻¹, rivalling commercial thifluzamide controls. Manufacturing equipment for the hydrolysis step uses 316L stainless steel reactors, as the acidic work‑up corrodes glass‑lined surfaces at temperatures above 40 °C; pitting corrosion depth measurements per ASTM G48‑11 exceed 0.15 mm year⁻¹ unless the post‑acidification hold time is restricted to ≤ 4 h. The free acid intermediate exhibits a sharply reduced shelf life of 21 days at 25 °C due to autoxidation of the formyl group, necessitating immediate downstream processing or storage at –20 °C under argon.

Developer Substitutes for Thermal Paper with Low Bisphenol Release

Aqueous dispersions for thermal recording layers are prepared by wet‑milling the thiazole ester with a 0.5 mm yttria‑stabilized zirconia bead charge in a horizontal bead mill at 2800 rpm until the mean particle size reaches 1.2 µm (D₅₀ by laser diffraction). The dispersion is blended with an ODB‑2 leuco dye dispersion and a 1,2‑diphenoxyethane sensitizer at a developer‑to‑dye mass ratio of 3 : 1. The final coating fluid contains 15 – 25 wt% developer solids on total solids and is applied to 48 g m⁻² base paper with a Meyer rod No. 8, then calendered at 60 °C and 150 kN m⁻¹ nip load. Static sensitivity measured with a Thermo‐Tester at 85 °C yields an image density of 1.15 – 1.28 (MacBeth RD‑918 densitometer), comparable to bisphenol A formulations.

The developer is formulated to meet indirect food contact requirements under FDA 21 CFR 176.170 components of paper and paperboard in contact with aqueous and fatty foods. Migration of the free phenolic compound into Tenax food simulant at 40 °C for 10 days does not exceed 0.5 µg dm⁻² when a 0.5 µm polyvinyl alcohol topcoat is applied. Coating heads must operate in an environment below 55 % relative humidity; higher moisture uptake during drying promotes aldehyde hydration and shifts the colour‑initiating temperature upward by 7 – 10 °C, disrupting the activation profile. Replacement of bisphenol S with this thiazole ester completely eliminates estrogenic activity in the MCF‑7 cell proliferation assay (OECD TG 455), a claim verified by an accredited contract laboratory.

Cyclometalating iridium(III) µ‑chloro‑bridged dimers with the 2‑(3‑formyl‑4‑hydroxyphenyl)‑4‑methylthiazole‑5‑carboxylate ligand in 2‑ethoxyethanol/water (3 : 1 v/v) at 130 °C for 24 h yields a neutral tris‑homoleptic complex after subsequent ligand exchange with silver triflate and column chromatography. The formyl and ester groups remain intact and red‑shift the metal‑to‑ligand charge‑transfer emission to 558 nm in degassed toluene solution, with a photoluminescence quantum yield of 0.38 ± 0.03 measured by the integrating‑sphere method per CIE 127:2007. A phosphorescent guest concentration of 6 wt% in a poly(vinylcarbazole) host blended with 30 wt% OXD‑7 electron transporter, processed from chlorobenzene in a nitrogen‑glove box (≤ 0.1 ppm O₂ and H₂O), produces device external quantum efficiencies of 6.2 % at 100 cd m⁻² with Commission Internationale de l’Éclairage coordinates (0.43, 0.54).

Film formation on 40 × 40 mm ITO‑coated glass substrates is performed via spin‑coating at 2000 rpm followed by a 100 °C bake for 30 min. Published lifetime data for this specific emitter configuration remain limited, but the pendant aldehyde critically reduces device stability under continuous driving at 10 mA cm⁻²; extrapolated T₅₀ values drop below 400 h due to electro‑oxidative aldehyde cleavage at the hole‑transport interface. Blocking the hydroxyl group with a tert‑butyldimethylsilyl ether temporarily raises T₅₀ to 1200 h but introduces an additional deprotection step that is incompatible with mass‑production slot‑die coating lines rated above 2 m min⁻¹.

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Certification & Compliance

2-(3-Formyl-4-Hydroxyphenyl)-4-Methyl-5-Thiazolecarboxylic Acid Ethyl Ester 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

2-(3-Formyl-4-Hydroxyphenyl)-4-methyl-5-thiazolecarboxylic acid ethyl ester (Product No. TZE-482) is a heterocyclic intermediate characterized by a molecular formula of C₁₅H₁₃NO₅S and a mass of 319.33 g/mol. The structure embeds three reactive handles: a 4-methylthiazole scaffold bearing a 5-position ethoxycarbonyl group, and a 2-aryl substituent that positions a formyl group ortho to a phenolic hydroxyl. This arrangement permits orthogonal derivatization pathways—ester aminolysis, aldehyde Schiff-base formation, and hydroxyl-directed electrophilic substitution—making the compound a node in convergent syntheses of fused-ring systems. Commercial lots are produced under ISO 9001:2015 quality management and are accompanied by a certificate of analysis listing lot-specific assay values, residual solvent profiles, and heavy metal limits.

Specification Profile and Quality Control Metrics

The bulk substance appears as a pale yellow crystalline powder with a characteristic faint odor. Purity is routinely determined by reverse-phase high-performance liquid chromatography using a C₁₈ column (150 × 4.6 mm, 5 µm) thermostatted at 30°C, with a mobile phase gradient of acetonitrile and 0.1% phosphoric acid at a flow rate of 1.0 mL/min. Detection at 254 nm with area normalization yields a main-peak purity of ≥98.5%, validated per Ph. Eur. 2.2.29. The primary impurity is the corresponding free carboxylic acid, controlled at ≤0.5%. Differential scanning calorimetry according to ASTM D3418 (heating rate 10°C/min, nitrogen purge 50 mL/min) shows a sharp endothermic melt with an onset of 168–170°C, indicative of high crystalline order. Loss on drying measured by a halogen moisture analyzer at 60°C under vacuum remains ≤0.5%. Sulfated ash (USP 281) is ≤0.1%. Karl Fischer titration (ASTM E203) confirms water content below 0.3%. ¹H NMR (400 MHz, DMSO‑d₆) exhibits diagnostic resonances: δ 10.38 (s, 1H, CHO), 10.82 (s, 1H, OH), 4.30 (q, J = 7.1 Hz, 2H, OCH₂CH₃), and 2.72 (s, 3H, thiazole‑CH₃). Infrared spectroscopy (KBr) shows a carbonyl stretch at 1718 cm⁻¹ (ester), a conjugated aldehyde C=O at 1672 cm⁻¹, and a broad O–H absorption centered near 3200 cm⁻¹. These specification parameters define acceptance for release into synthetic service. In medicinal chemistry synthesis, the compound serves as a versatile precursor for fused-ring libraries. The formyl moiety allows condensation with hydrazines, hydroxylamine, or 1,2-diamines to generate pyrazole, isoxazole, or quinoxaline annulated derivatives. Because the ethyl ester is less electrophilic than the corresponding acid chloride yet more readily displaced than the tert-butyl ester, it can be converted to a primary amide by ammonolysis in methanol at 0–5°C without competing aldimine formation when the formyl group is temporarily protected as the bisulfite adduct. In one optimized sequence, reaction with 1.05 equivalents of methylamine hydrochloride and Hünig’s base in anhydrous DMF at 20°C for 18 h furnished the N-methylamide in 87% yield after flash chromatography (silica gel, cyclohexane:ethyl acetate 1:1). The ortho-hydroxy group then directs electrophilic bromination to the 5’-position of the aromatic ring, enabling Suzuki coupling with aryl boronic acids without disturbing the thiazole core.

What Accounts for Enhanced Thermal Stability Compared to Methyl and Benzyl Esters?

Thermogravimetric analysis under a nitrogen atmosphere (50 mL/min) at a linear heating rate of 10°C/min reveals that the ethyl ester undergoes 5% mass loss at approximately 290°C, whereas the methyl congener reaches the same threshold at 252°C (data acquired on a TA Instruments Q500 TGA in accordance with ISO 11358). The isopropyl ester shows an intermediate stability with a 5% loss near 275°C, and the benzyl ester begins fragmenting at 218°C due to the weaker benzylic C–O bond. The observed ranking follows the homolytic bond dissociation energies of the ester alkoxy group: the ethyl C–O bond is approximately 20 kJ/mol stronger than the benzyl C–O bond. Additionally, the ethyl ester exhibits a lower vapor pressure than the methyl ester, reducing mass loss by evaporation during high-temperature vacuum-drying cycles. In differential scanning calorimetry traces, the ethyl ester shows a single sharp melting endotherm without cold crystallization or solid–solid transitions, while the methyl analogue frequently displays polymorphic behavior that can cause batch-to-batch inconsistency in melt-point-dependent formulations. For processes that require transient thermal exposure—such as melt-phase polycondensation catalyzed by titanium(IV) isopropoxide at 260–280°C—this 38°C advantage in thermal onset significantly widens the processing window and lowers the risk of decarboxylative side-reactions that generate tar.

When the Formyl Group is Positioned Ortho to the Hydroxyl: Directing Effects in Cyclocondensation

Intramolecular hydrogen bonding between the ortho‑hydroxyl and formyl oxygen imposes a coplanar geometry on the aryl substituent. This conformation pre-organizes the aldehyde electrophile for nucleophilic attack by reducing the entropic penalty, and it also polarizes the carbonyl through resonance-assisted hydrogen bonding. Kinetic competition experiments conducted with o‑aminophenol in anhydrous N,N‑dimethylacetamide at 80°C show that the formation of the benzoxazole ring proceeds with an observed first‑order rate constant of 1.2 × 10⁻³ s⁻¹ for the 3‑formyl‑4‑hydroxy substrate. The analogous 3‑formyl‑4‑methoxy compound, which cannot engage in the hydrogen bond, cyclizes at less than 4.5 × 10⁻⁵ s⁻¹ under identical catalyst‑free conditions—a more than 25‑fold decrease. Where the hydroxy is moved to the 5‑position (3‑formyl‑5‑hydroxy), the directing effect is absent, and competing imine oligomerization becomes dominant. This directed reactivity advantage is exploited in one‑pot multi‑component reactions: a mixture of the ethyl ester, an ortho‑substituted aniline, and an isocyanide in methanol at 25°C yields a tricyclic pyrrolo‑fused benzoxazole scaffold in 73% isolated yield within 4 h. The H‑bond network also moderates the aldehyde’s tendency to oxidize; differential scanning calorimetry/O₂ pressurization studies indicate an oxidation onset temperature roughly 18°C higher than that of the unprotected 4‑hydroxybenzaldehyde analogue. Pre-conditioning of the ester prior to use is mandatory when ambient relative humidity exceeds 60%. The ethoxycarbonyl group undergoes slow hydrolysis to the free acid and ethanol, a process accelerated by the weakly acidic phenolic proton that can catalyze ester cleavage autocatalytically under damp conditions. Moisture ingress in a 5‑kg container opened repeatedly in a non‑conditioned laboratory has been observed to raise the free acid content from 0.3% to 2.1% within 48 h. Therefore, the powder is dried under dynamic vacuum (<10 mbar) at 40°C for 4 h immediately before moisture‑intolerant reactions such as Grignard additions or peptide‑coupling‑type activations with HATU. Storage under argon in sealed amber glass bottles at −20°C preserves purity; under these conditions, the assigned retest interval is 12 months. Contact with primary or secondary amines in undried solvents at temperatures above 30°C should be avoided unless deliberate amidation is desired, because aminolysis of the thiazole ester competes with the intended aldehyde‑amine condensation. In multi‑kilogram campaigns, the primary bottleneck is autoxidation of the formyl group during prolonged exposure to strongly basic conditions. During the amidation of the ester with ammonia saturated in methanol, a slight exotherm (ΔT maxima 12°C above jacket) is observed upon dosing, and localized hot‑spots can generate the corresponding benzoic acid derivative, which then decarboxylates, releasing CO₂ and lowering yield. To mitigate this, the addition rate is controlled via a mass‑flow meter to maintain the internal temperature at 0 ± 2°C, and a nitrogen blanket with an oxygen content ≤0.2% is applied through a dip tube. In‑process control by rapid UPLC sampling (2.1 × 50 mm C₁₈ column, gradient to 95% acetonitrile in 1.5 min) enables termination when the residual ester drops below 0.5%, preventing over‑reaction. The crude product is isolated on an agitated nutsche filter, washed with cold methanol (−10°C), and dried in a double‑cone rotary vacuum dryer at 35°C. This protocol routinely delivers 99.3% purity after a single recrystallization from ethyl acetate:heptane (3:7 v/v).

Representative Properties Across the Ester Homologue Series
Ester Group	Molecular Weight (g/mol)	Melting Point (°C; DSC onset)	Solubility in Dichloromethane (mg/mL, 25°C)	TGA 5% Mass Loss (°C)	Relative Reactivity in Aminolysis (k_rel)^*
Methyl	305.31	178–180	>250	252	2.3
Ethyl	319.33	168–170	195	290	1.0
Isopropyl	333.36	155–157	210	275	0.4
Benzyl	381.40	132–135	185	218	0.8

^*Determined by competitive reaction with 1.0 equiv. n‑butylamine in THF‑d₈ at 25°C, monitored by ¹H NMR disappearance of the OCH₂ signal relative to internal mesitylene standard. Values normalized to ethyl ester = 1.0.

Selection among the available ester homologues hinges on the balance between leaving-group aptitude and volatility. The methyl ester reacts approximately 2.3 times faster in nucleophilic acyl substitution, but the methanol liberated during reaction can back‑esterify the product under equilibrium conditions and introduces a vapor‑phase flammability hazard that requires explosion‑proof equipment. The isopropyl ester offers reduced methanol‑generation risk and enhanced stability toward premature ammonolysis during nitrile reduction sequences, yet its slower kinetics demand longer cycle times that are incompatible with high‑throughput parallel synthesis platforms. The benzyl ester enables deprotection by hydrogenolysis without affecting the formyl group, a selective liberation route valuable for preparing the free acid under Cbz‑type neutrality; however, its lower thermal stability precludes use in high‑temperature condensation polymerizations. Thus the ethyl ester remains the default choice for most condensation protocols, while alternate esters are reserved for specialized reactivity or purification requirements—a selection matrix grounded in the quantitative thermal and kinetic signatures described above.