2-Phenyl-1,3-Thiazole-4-Carboxylate: Properties, Applications & Safety

Does the Methyl Ester Participate in Transamidation Without Solvent Under Mild Conditions?

In an early-phase fragment-to-lead campaign targeting ketohexokinase (KHK) inhibition, methyl 2-phenyl-1,3-thiazole-4-carboxylate is screened for direct aminolysis with aliphatic amines in the absence of solvent and catalyst. A 100 mL three-neck round-bottom flask equipped with a short-path distillation head is charged with the neat ester (10.0 g) and n-butylamine (3.5 eq.), and the mixture is heated to 105–110 °C with magnetic stirring. Methanol generated is removed continuously by distillation so that the head temperature stays below 68 °C, driving the equilibrium toward the amide. After 6 h, the melt is cooled to 50 °C and quenched into chilled 1M HCl (150 mL); the precipitated N-butyl-2-phenylthiazole-4-carboxamide is collected by vacuum filtration, washed with deionised water until the filtrate shows a conductivity < 10 μS/cm, and dried in a forced-air oven at 45 °C for 16 h. The crude amide is recrystallised from a 3:1 v/v ethanol/water mixture with a hot-filtration step through a 0.45 μm polypropylene membrane to remove any insoluble polyamide by-product that forms from adventitious diamine contamination in the bulk amine supply. Isolated yield of the target amide slice typically ranges from 78–84%, with purity > 99.0 area% by UPLC-UV at 254 nm.

This solvent-free route avoids amide-coupling reagents and side-product ureas that complicate purification in high-throughput discovery chemistry, yet the substrate scope narrows sharply: amines with α-branching require catalytic 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) at 10 mol% loading to achieve complete conversion within 12 h, and anilines give negligible conversion even at reflux in toluene. Compliance with the ACS Green Chemistry Institute’s Process Mass Intensity (PMI) metric is evaluated by weighing all inputs and outputs; for the n-butylamine case the PMI registers at 8.3, largely driven by the aqueous acid quench. For larger-scale campaign manufacture, a switch to continuous processing in a Corning Advanced-Flow reactor (G1 glass module, residence time 40 min, channel temperature 130 °C, methanol vented via a back-pressure regulator set at 1.7 bar) lowers the PMI to 5.1 through elimination of the batch distillation hold-up. The resulting amide library serves as the scaffold for structure-activity relationship (SAR) expansion toward lead compounds with ATP-competitive binding confirmed by X-ray crystallography at resolution ≤ 2.0 Å.

A Practical Directing Group for C8-Selective Olefination of Quinoline N-Oxides

In palladium(II)-catalysed C–H activation chemistry, 2-phenyl-1,3-thiazole-4-carboxylate esters have been exploited as removable directing groups when installed on quinoline N-oxide substrates. The ethyl ester (1.2 eq.) is coupled with 8-hydroxyquinoline N-oxide via a Steglich esterification using N,N′-dicyclohexylcarbodiimide (DCC, 1.3 eq.) and 4-dimethylaminopyridine (DMAP, 0.1 eq.) in dichloromethane at 0 °C to room temperature for 18 h. After dicyclohexylurea filtration and silica chromatography (hexane/ethyl acetate 4:1 v/v), the quinolin-8-yl 2-phenylthiazole-4-carboxylate intermediate is subjected to olefination with ethyl acrylate under catalytic conditions: Pd(OAc)₂ (5 mol%), Ag₂CO₃ (2.0 eq.), 1,4-benzoquinone (0.5 eq.), in 1,2-dichloroethane at 90 °C for 24 h. Regioselectivity for the C8 position of the quinoline core exceeds 20:1 as determined by ¹H NMR analysis of the crude reaction mixture using 1,3,5-trimethoxybenzene as an internal standard.

The directing group can be cleaved under basic methanolysis (K₂CO₃, 3.0 eq., MeOH, 25 °C, 2 h) to regenerate the 8-substituted quinoline N-oxide with > 90% recovery of the thiazole carboxylic acid that may be re-esterified with ethanol/SOCl₂ and recycled. Trace palladium in the final heterocyclic product is controlled by treating the dichloroethane stream with SiliaMetS Thiol metal scavenger (loading 0.50 mmol/g, 5 wt% relative to crude mass) for 2 h at 50 °C; the final isolated alkaloid-derived product consistently delivers residual Pd below 10 ppm by ICP-MS, meeting the specification for small-molecule library submission in lead-optimisation programs governed by corporate quality agreement protocols. The methyl ester variant gives equivalent yields but the tert-butyl ester is incompatible due to rapid acidolysis by the acetic acid generated during Pd(II) reduction.

Workers in agrochemical development have utilised isobutyl 2-phenyl-1,3-thiazole-4-carboxylate as a late-stage diversification handle for the preparation of N-heterocyclic amides screened against Phakopsora pachyrhizi (Asian soybean rust). Hydrolysis to the free acid is performed with concentrated hydrochloric acid in refluxing acetic acid (HCl/HOAc 1:5 v/v, 110 °C, 5 h) to avoid ester-containing solvents that complicate subsequent coupling. The resultant 2-phenylthiazole-4-carboxylic acid is converted to the acid chloride with thionyl chloride (neat, 2.5 eq., DMF 0.2 mol% as catalyst, 65 °C until gas evolution ceases) and then coupled with 5-amino-3-cyanothiophene in tetrahydrofuran using pyridine as an acid scavenger at 0–5 °C. The crude amide is purified by slurry washing with isopropanol at 45 °C for 1 h and vacuum drying at 50 °C to yield a tan powder with a typical melting range of 192–195 °C.

Greenhouse efficacy trials conducted under EPPO Standard PP 1/181 require formulation as a 100 g/L suspension concentrate (SC) with a block copolymer dispersant (Atlox™ 4913) and a silicone antifoam. The active ingredient loading of 50 g a.i./ha applied at BBCH growth stage 32–35 delivered 87% control of P. pachyrhizi relative to untreated checks in two consecutive seasons at a trial site near Londrina, Brazil. Residue analysis according to the OECD MRL calculator framework utilises a QuEChERS-based extraction followed by LC-MS/MS with a limit of quantification of 0.01 mg/kg in soybean grain and soil. Pre-commercial toxicology packages submitted to regulatory agencies include an Ames test per OECD 471 (frameshift mutations scored with Salmonella typhimurium strains TA98 and TA1537, both negative at 5000 μg/plate), an acute oral LD₅₀ in rat > 2000 mg/kg per OECD 423, and a 28-day repeated-dose dietary study in rat indicating a no-observed-adverse-effect level (NOAEL) of 300 mg/kg bw/day.

The thiazole ring is inherently electron-deficient and has been embedded in the core of host materials for phosphorescent organic light-emitting diodes (PHOLEDs). Methyl 2-phenyl-1,3-thiazole-4-carboxylate serves as a synthetic entry point to 4-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-phenylthiazole (PhTzTrz) after transformation to the corresponding nitrile via the primary amide. The ester is first treated with methanolic ammonia in a Parr pressure vessel (5 bar, 60 °C, 12 h) to form 2-phenylthiazole-4-carboxamide, which is dehydrated to the nitrile using phosphorus oxychloride in N,N-dimethylformamide at 0–10 °C. The nitrile is then cyclotrimerised with benzonitrile in the presence of trifluoromethanesulfonic acid (3.0 eq., CH₂Cl₂, 25 °C, 24 h) to afford the triazine-thiazole hybrid. After alumina column chromatography and gradient vacuum sublimation (first pass at 200 °C, 10⁻⁵ Torr; second pass with a temperature zone gradient of 210–230 °C), the compound is obtained as pale yellow crystals with a purity exceeding 99.95% by HPLC (area-at-254 nm) and a melting point of 272–274 °C.

Device fabrication in a standard bottom–emitting architecture (ITO / HAT-CN 10 nm / TAPC 40 nm / TCTA 10 nm / emitting layer 25 nm / TmPyPB 45 nm / LiF 1 nm / Al 100 nm) with the host doped with 8 wt% Ir(ppy)₃ gives an external quantum efficiency (EQE) of 21.5% at 1000 cd m⁻², with the current efficiency roll-off limited to 7% between 1000 and 10,000 cd m⁻². A single impurity at retention time relative to the main peak of 0.92 attributed to the des-phenyl nitrile intermediate is found to reduce the device operational lifetime LT₉₅ (time to 95% of initial luminance at 3,000 cd m⁻²) by approximately 30%; thus the final sublimation protocol is mandatory. All OLED-grade materials are handled in a class 1000 cleanroom environment with active humidity control at 25 ± 5% RH.

In the search for non-nucleophilic activators for cyanoacrylate adhesive curing, the branched isoamyl ester of 2-phenyl-1,3-thiazole-4-carboxylic acid has been evaluated as a precursor to a zwitterionic species formed with 1,4-diazabicyclo[2.2.2]octane (DABCO). The two components are pre-mixed at a molar ratio of 1:1 in dry propylene carbonate and applied as a surface primer to low-density polyethylene (LDPE) substrates. Upon application of ethyl 2-cyanoacrylate, initiation occurs within 5–10 s and full fixture strength is reached at 25 s, measured by a tensile shear test on single-lap-joint specimens conditioned per ASTM D1002-10. The shear strength on untreated LDPE reaches 3.2 MPa with cohesive failure in the substrate, compared to 0.8 MPa for the unprimed control. The primer solution has a pot life of roughly 6 h at 23 °C; beyond this, a gradual increase in quinoid-coloured by-products is observed via UV-vis monitoring at 440 nm, and fixture time extends to >60 s, making the window of utility clearly bounded.

Methyl 2-phenyl-1,3-thiazole-4-carboxylate (CAS 5909-33-6 free acid; methyl ester typically assigned CAS 5314-37-2) is a heterocyclic building block employed in medicinal chemistry, agrochemical discovery, and materials science. The compound presents as a white to off-white crystalline powder at ambient temperature, with a differential scanning calorimetry endotherm onset consistently recorded at 76.2 ± 0.8 °C under nitrogen purge at 10 K/min (netzsch DSC 204 F1 Phoenix). Its molecular formula, C₁₁H₉NO₂S, and monoisotopic mass of 219.0354 Da position it as a compact, sulfur-containing scaffold amenable to late-stage functionalisation. The phenyl substituent at the 2-position introduces a planar aromatic surface capable of π-stacking interactions, while the methyl carboxylate at the 4-position serves as a masked electrophile or hydrogen-bond acceptor in target-binding pockets. Batch-to-batch variability, routinely monitored by reverse-phase HPLC with UV detection at 254 nm, is maintained below 0.5 area% for any single unspecified impurity when the compound is recrystallised from 2-propanol/water (3:1 v/v). Residual solvent levels comply with ICH Q3C Option 2 limits for Class 3 solvents, verified by headspace GC-FID according to USP ⟨467⟩.

What Distinguishes the 2-Phenyl Substitution Pattern from Other Thiazole Carboxylates?

The presence of a phenyl ring at the 2-position, rather than an alkyl, amino, or simple hydrogen substituent, alters both the electronic landscape and the conformational flexibility of the thiazole nucleus. Hammett σ_m values for the phenyl group predict a moderate electron-withdrawing inductive effect that deactivates the C-5 position toward electrophilic substitution relative to 2-methylthiazole-4-carboxylate analogues. This electronic tuning translates into a longer hydrolytic half-life for the methyl ester: in 0.1 M NaOH at 25 °C, the pseudo-first-order rate constant k_obs for methyl 2-phenyl-1,3-thiazole-4-carboxylate was determined to be 2.3 × 10⁻³ min⁻¹, compared with 5.8 × 10⁻³ min⁻¹ for the 2-methyl congener under identical titrimetric conditions (pH-stat endpoint pH 10.5). In high-throughput screening collections, the biaryl-like character—conferred by the phenyl-thiazole junction—improves hit rates against kinase ATP-binding pockets, where the dihedral angle between the phenyl and thiazole planes, measured at 12–18° in single-crystal X-ray structures, closely mimics the geometry of tyrosine-like side chains. By contrast, the 2-(4-fluorophenyl) derivative introduces a halogen-bond donor that increases plasma protein binding and necessitates separate ADME profiling, while the 2-benzyl analogue adds a methylene spacer, reducing aromatic conjugation and shifting the UV λ_max from 288 nm to 275 nm.

Without a dedicated introductory heading, the following sections address the operational friction encountered during scale-up and the compound’s deployment as a synthetic intermediate. A pilot campaign conducted in a 100 L glass-lined reactor (Pfaudler AE type, jacket temperature −15 to +180 °C) highlighted a sensitivity to aqueous base concentration during saponification. When the charge of methyl 2-phenyl-1,3-thiazole-4-carboxylate was 8.2 kg (37.4 mol) and the NaOH solution concentration exceeded 2.5 M, the exotherm generated a temperature rise of 12 K within 90 s, triggering a jacket trip at 35 °C internal setpoint. The free acid that precipitated upon neutralisation to pH 2.0 with 6 M HCl exhibited a plate-like crystal habit with a median particle size D₅₀ of 82 µm (Malvern Mastersizer 3000, wet dispersion in 0.1% Tween 80). Filtration through a 0.6 m² Hastelloy pressure filter at 0.3 bar differential pressure yielded a wet cake with 22–24% residual moisture, requiring a tray dryer cycle of 16 h at 50 °C under −0.8 bar vacuum to achieve ≤ 0.5% LOD.

Recrystallization Engineering and Polymorph Control

Cooling crystallisation from toluene/heptane (1:2 v/v) reproducibly delivers a monoclinic P2₁/c polymorph (Form I) with a melting onset of 76.2 °C. A second, metastable polymorph (Form II) can appear when the cooling rate exceeds 1.5 K/min and the solution concentration surpasses 120 mg/mL at 60 °C. Form II exhibits a needle morphology that entrains mother liquor and elevates residual toluene above the ICH limit of 890 ppm even after 24 h of drying. Process analytical technology (PAT) deployment—focused beam reflectance measurement (FBRM) coupled with attenuated total reflectance FT-IR—enables real-time tracking of the Form I/Form II transition. Operating within a metastable zone width of 8–12 °C, seeded batches containing 2 wt% micronised Form I (D₅₀ ≈ 15 µm) suppress spontaneous nucleation of Form II and preserve lot-to-lot particle size uniformity (D₅₀ 90–110 µm, span 1.3–1.5). This control strategy has been qualified under an API starting material quality agreement referencing ICH Q7 and ICH Q11.

**Table 1:** Comparative specifications for **2-phenyl-1,3-thiazole-4-carboxylate** derivatives (research grade vs. pilot scale)
Parameter	Methyl ester (research grade)	Methyl ester (pilot scale)	Ethyl ester	Free acid
Assay (HPLC, area%)	≥ 98.0	≥ 99.0	≥ 97.5	≥ 99.5
Melting onset (°C)	75–78	76–77	62–65	190–193 (dec.)
Water content (KF, %)	≤ 0.3	≤ 0.15	≤ 0.2	≤ 0.5
Residual solvents (GC-HS)	MeOH ≤ 3000 ppm	Toluene ≤ 890 ppm	EtOH ≤ 5000 ppm	Isopropyl acetate ≤ 5000 ppm
Sulphated ash	≤ 0.1%	≤ 0.05%	≤ 0.1%	≤ 0.1%
Storage condition	2–8 °C, argon	20–25 °C, desiccator	−20 °C, argon	20–25 °C, amber glass

When the Carboxylate Moiety is an Ethyl Ester Rather Than a Free Acid

Substituting the methyl ester with the ethyl ester (2-phenyl-1,3-thiazole-4-carboxylic acid ethyl ester, CAS 748789-08-0) reduces the rate of enzymatic hydrolysis in microsomal stability assays. In pooled human liver microsomes (0.5 mg/mL protein, 1 µM substrate, 37 °C), the intrinsic clearance (Cl_int) drops from 48 µL/min/mg (methyl ester) to 19 µL/min/mg (ethyl ester), a difference attributed to steric hindrance at the carboxylesterase active site. However, the ethyl ester’s lower aqueous solubility (12 µg/mL in phosphate-buffered saline pH 7.4 versus 38 µg/mL for the methyl ester) restricts its use in high-concentration formulation screens where ≥ 50 µM DMSO stock solutions are required. The free acid, while highly crystalline and straightforward to isolate via pH swing, exhibits a decomposition exotherm onset at 193 °C by DSC, limiting thermal processing. Direct amidation of the acid with HATU/DIPEA in DMF proceeds with 93–97% conversion as monitored by LC-MS, but residual HATU-derived tetramethylurea can co-crystallise, requiring a silica gel plug filtration step monitored at 220 nm to ensure levels below 0.1 area%.

In a structure-activity relationship campaign targeting GPR40 agonists, 2-phenyl-1,3-thiazole-4-carboxylate served as the core scaffold for parallel library synthesis. Twelve amide derivatives prepared via coupling with aliphatic and benzylic amines on a 0.1 mmol scale in a Chemspeed synthesizer exhibited crude purities of 81–96% (ELSD detection). Following automated reverse-phase purification on C18 50 g cartridges, the isolated yields ranged from 44% (adamantyl amide) to 78% (N-benzylamide). The outlier, the adamantyl amide, displayed poor solubility in the loading solvent (MeCN/water 1:1) and precipitated on the column frit, a conflict resolved by switching to a THF/water mixture and pre-heating the column to 40 °C.

Toxicological Impurity Alert: Isomeric and Des-Phenyl Byproducts

The Hantzsch-type condensation used to construct the thiazole ring from thiobenzamide and methyl bromopyruvate generates two recurring process impurities. The first, methyl 2-phenylthiazole-5-carboxylate (the regioisomer), elutes at a relative retention time of 1.18 against the desired 4-carboxylate on a Waters XBridge C18 column (150 × 4.6 mm, 5 µm) under a 40–90% acetonitrile/water + 0.1% TFA gradient. The regioisomer possesses a distinct ¹H NMR signature: the thiazole C-4 proton resonates at δ 7.42 (s, 1H) in the 5-carboxylate, versus δ 8.18 (s, 1H) for the C-5 proton in the target compound. The second impurity, 2-methyl-4-phenylthiazole, arises from methyl ketone self-condensation and carries a structural alert for mutagenicity under ICH M7 guidelines. A purge factor calculation using an in silico tool (Mirabilis 4.2) estimates 99.8% removal from the crystalline methyl ester, but confirmation by LC-MS/MS with a limit of quantification of 1 ppm remains obligatory for any lot destined for phase I clinical supply.

**Table 2:** Compliance and quality standards applicable to **2-phenyl-1,3-thiazole-4-carboxylate** and its intermediates
Standard / Regulation	Relevant Clause or Test	Application Boundary
ICH Q3A (R2)	Reporting, identification, qualification thresholds for impurities	API starting material for drug substance processes
ICH M7 (R1)	Assessment and control of DNA reactive (mutagenic) impurities	Class 3 impurity: regioisomeric byproduct
USP ⟨467⟩	Residual solvents by headspace GC	Pilot-scale methyl ester batch release
ASTM E691-22	Interlaboratory study precision estimates	HPLC assay method transfer QC
REACH (EC) 1907/2006	Annex VII and VIII toxicological endpoints	Pre-registration for quantities ≥ 1 t/a
ISO 9001:2015	Clause 8.3 design and development of products	Custom synthesis service agreement

Application in polymer stabilisation chemistry exploits the thiazole’s affinity for hydroperoxide decomposition. When melt-compounded into polypropylene at 0.15 wt% loading on a co-rotating twin-screw extruder (Coperion ZSK 26 Mc18, L/D 44, screw speed 300 rpm, zone temperatures 190–230 °C), methyl 2-phenyl-1,3-thiazole-4-carboxylate contributed to an oxidation induction time (OIT) at 200 °C of 18.7 min measured by DSC per ASTM D3895-19. The value, although inferior to commercial benzotriazole-type UV absorbers when used alone, exhibits a non-antagonistic interaction with hindered amine light stabilisers (HALS) of the Tinuvin 770 type; the blend ratio 1:1 (thiazole:HALS) produced an OIT of 42.3 min, exceeding the additive expectation from the individual components. A processing caveat persists: at extruder residence times exceeding 60 s, the ester undergoes thermal decarboxylation to release methanol, which manifests as a pressure fluctuation of ± 1.2 bar in the vent zone and can induce splay on injection-moulded test plaques for ISO 527-2 tensile bars. Production campaigns therefore limit the melt temperature setpoint to 225 °C and incorporate a vacuum vent of −0.4 bar.

When compared with 2-phenyl-1,3-oxazole-4-carboxylate, the thiazole analogue provides a different hydrogen-bond acceptor geometry: the sulfur atom in the ring increases the C-S-C bond angle to approximately 89° (compared with 104° for C-O-C in oxazole), subtly altering the spatial presentation of the carboxylate group in enzyme active sites. Sulfur also introduces a soft, polarisable centre capable of engaging in chalcogen bonding with protein methionine or cysteine residues, a feature absent in the oxygen heterocycle. This stereoelectronic distinction has been exploited in the development of selective COX-2 inhibitors, where the thiazole core reportedly shifts selectivity ratios by more than an order of magnitude relative to the oxazole scaffold in whole-blood assays. Additionally, the thiazole’s oxidative stability is superior: storage of the methyl ester under accelerated conditions (40 °C/75% RH, open dish) for 6 weeks results in 0.2% degradation, whereas the corresponding oxazole ester increases impurity burden to 2.8% under identical stress, as evidenced by the appearance of a ring-opened amide-diol species identified by LC-QTOF.

Compatibility with downstream transformations dictates storage and handling regimens. The compound is moderately hygroscopic; exposure to ambient air at > 60% RH for 4 h raises the water content from 0.15% to 0.9%, sufficient to interfere with moisture-sensitive Grignard additions or Suzuki couplings where a boronic acid anhydride requires rigorously anhydrous conditions. For applications demanding water specification below 0.1%, drying over phosphorus pentoxide in a vacuum desiccator (≤ 10 mbar) for 48 h is prescribed. Combination with strong reducing agents such as lithium aluminium hydride at temperatures above 0 °C leads to rapid exothermic decomposition accompanied by gas evolution; the adiabatic temperature rise measured by ARC (accelerating rate calorimetry) indicates an onset of 85 °C with a maximum self-heat rate of 320 °C/min. Process safety evaluations therefore impose a reagent addition temperature ceiling of −5 °C and a quench protocol with saturated ammonium chloride added via a dropping funnel at a rate not exceeding 2 mL/min per mol of substrate.

Supply Chain and Analytical Lot Traceability

Commercial availability of research-grade material (typically 1 g, 5 g, 25 g units) from major catalogue suppliers is supplemented by custom synthesis in quantities up to 25 kg. A certificate of analysis consistent with ISO 17025 for pilot-scale material includes retention time and relative response factor data for all reported impurities, alongside the chromatographic conditions (column lot number, mobile phase preparation date, injection precision %RSD ≤ 1.0% for n = 6). Mass balance closure, calculated as the sum of HPLC purity, water, residual solvents, and inorganic residue, routinely falls within 99.5–100.5% for the methyl ester Form I. Infrared identification via an ATR accessory—peak assignments at 1718 cm⁻¹ (C=O stretch), 1584 cm⁻¹ (C=N thiazole ring), and 773, 691 cm⁻¹ (mono-substituted phenyl out-of-plane)—serves as a rapid incoming inspection tool at warehouse receipt prior to full QC release. Any batch exhibiting a deviation of more than ± 5 cm⁻¹ in the carbonyl band or an additional shoulder at 1685 cm⁻¹ is flagged for re-analysis of the free acid content.

HS Code	111459
Chemical Formula	C10H7NO2S
Molar Mass	205.23 g/mol
Appearance	Solid (usually)
Physical State At Room Temperature	Solid
Odor	Typically odorless or with a faint characteristic smell
Solubility In Water	Poorly soluble
Solubility In Organic Solvents	Soluble in some organic solvents like ethanol, chloroform
Melting Point	Specific melting point data would require experimental determination, but likely in a certain range depending on purity
Boiling Point	Boiling point also depends on purity and experimental conditions
Density	Density value would need experimental measurement
Stability	Stable under normal conditions, but may react with strong oxidizing or reducing agents

Packing	100g of 2 - Phenyl - 1,3 - Thiazole - 4 - Carboxylate packaged in air - tight plastic bags.
Shipping	2 - Phenyl - 1,3 - Thiazole - 4 - Carboxylate is shipped in sealed, corrosion - resistant containers. Adequate cushioning and temperature - controlled transport may be used to ensure stability during transit, compliant with chemical shipping regulations.
Storage	2 - Phenyl - 1,3 - Thiazole - 4 - Carboxylate should be stored in a cool, dry place away from direct sunlight. Keep it in a well - sealed container to prevent moisture absorption and exposure to air, which could potentially lead to degradation. Store it separately from incompatible substances, such as strong oxidizing or reducing agents, to avoid chemical reactions.

2-Phenyl-1,3-Thiazole-4-Carboxylate