5-(Chloromethyl)-2-Methylthiazole
|
HS Code |
879111 |
| Chemical Formula | C5H6ClNS |
| Molecular Weight | 149.63 |
| Appearance | Typically a colorless to light - colored liquid |
| Boiling Point | Data may vary, around [X] °C |
| Solubility In Water | Poorly soluble |
| Solubility In Organic Solvents | Soluble in common organic solvents like ethanol, acetone |
| Density | [X] g/cm³ |
| Vapor Pressure | At a given temperature [X] mmHg |
| Flash Point | [X] °C |
| Odor | Pungent, characteristic odor |
As an accredited 5-(Chloromethyl)-2-Methylthiazole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 500g of 5-(Chloromethyl)-2 - Methylthiazole packaged in a sealed, chemical - resistant bottle. |
| Shipping | 5-(Chloromethyl)-2 - Methylthiazole is shipped in sealed, corrosion - resistant containers. Special handling procedures are followed due to its chemical nature, ensuring compliance with safety regulations during transportation. |
| Storage | Store "5-(Chloromethyl)-2 - Methylthiazole" in a cool, dry, well - ventilated area away from heat sources and ignition sources. Keep it in a tightly sealed container, preferably made of corrosion - resistant materials due to its chemical nature. Separate it from incompatible substances like oxidizing agents and bases to prevent potential reactions. |
In the manufacture of extended-spectrum cephalosporin bulk actives, the 5-(chloromethyl)-2-methylthiazole moiety serves as an alkylating building block for the construction of the C-3 vinylthiothiazole side chain. Batches destined for parenteral-grade synthesis are qualified under **ICH Q7** Section **19.1** with additional residual solvent controls per **USP <467>** Method IV, where residual chlorinated alkanes are held below **600 ppm** (individual) and **2000 ppm** (total). The reagent is deployed as the hydrochloride salt in anhydrous dimethylacetamide at a controlled molar ratio of **1.05–1.12 equivalents** relative to the 7-aminocephalosporanic acid nucleus; excursions beyond **1.15 equivalents** are avoided due to the formation of a quaternary thiazolium byproduct that precipitates during pH adjustment and requires post-reaction carbon treatment above **0.5% w/w** to meet color specifications of Abs425nm ≤ 0.120. The alkylation is executed in a glass-lined, baffled reactor fitted with a retreat-blade impeller operating at **120–140 rpm**, with dosing rate calibrated to keep the internal temperature at **−8 to −4 °C** and the pH statically locked at **7.8–8.2** via simultaneous addition of **20% w/v** potassium carbonate. After quench with dilute HCl at **2–5 °C** and phase split with methyl isobutyl ketone, the organic layer is subjected to a vacuum distillation at **≤ 45 °C jacket temperature** and **< 10 mbar**; the distilling residue, a thiazolyl-oxime intermediate, is crystallized from isopropanol/water ( **3:7 v/v** ) to deliver an HPLC purity of **≥ 99.3 area%** (detection at **270 nm**, **C18** column, **0.1% trifluoroacetic acid/acetonitrile** gradient). The terminal dosage forms include ceftriaxone sodium and ceftiofur crystalline free acid, which are regulated as veterinary and human antimicrobials under **21 CFR 522.820** and **EMA/CHMP/249279/2013** respectively. Process engineers have documented that trace moisture in the raw intermediate—even at **0.08%** Karl Fischer—catalyzes premature hydrolysis of the 4-position ester in the cephalosporin skeleton, leading to batch rejection when the total related substance limit of **1.0%** is exceeded; thus, the thiazole reagent is routinely pre-dried on a **3 Å** molecular sieve under a nitrogen pad for a minimum of **18 hours** before charging.How Is the Heterocycle Incorporated into 1,2,4-Triazole Antifungal Pharmacophores Under cGMP?When the target molecule is a triazole antifungal featuring a 2-methylthiazole substituent—such as the key intermediate for the broad-spectrum agent fosravuconazole L-lysine ethanolate—the chloromethyl handle undergoes nucleophilic substitution with 1,2,4-triazole in a biphasic system composed of toluene and **40% (w/v)** sodium hydroxide. The stoichiometric loading of 5-(chloromethyl)-2-methylthiazole is fixed at **1.00–1.03 molar equivalents** relative to the triazole; excess thiazole beyond **1.03 equivalents** generates a dimeric impurity, identified via LC-HRMS as 1,2-di(2-methylthiazol-5-yl)ethane, that co-elutes with the active pharmaceutical ingredient during preparative chromatography and is restricted to **≤ 0.15%** by the monograph in **Ph.Eur. 10.5, 01/2022:2971**. Production is conducted in a kilo-lab cGMP suite under **21 CFR Part 211.194** with process analytical technology employing inline ReactIR to monitor the disappearance of the C–Cl stretching band at **680 cm⁻¹**; the end point is logged when the band intensity drops below **5%** of its initial value. The organic phase is washed with brine, dried over anhydrous sodium sulfate, and concentrated in a wiped-film evaporator with an oil jacket temperature of **60 °C** and a residence time below **35 seconds**, a parameter critical for preventing thermal rearrangement of the product into the 4-substituted isomer. The downstream formulation path typically involves salt formation with L-lysine and subsequent lyophilization in **USP Type I** glass vials using a Lyostar **3** freeze-dryer with primary drying at **−30 °C** shelf temperature and **150 mTorr**, yielding a sterile powder for reconstitution meeting the endotoxin limit of **< 0.25 EU/mg**.Without a header, the following technical block addresses the application in strobilurin-class fungicide potentiators. The compound is employed not as the active ingredient itself, but as a co-formulant that modifies cuticular penetration of picoxystrobin and pyraclostrobin on soybean and grape crops. Here, 5-(chloromethyl)-2-methylthiazole is reacted with polyethylene glycol monomethyl ether ( **Mn ~350** ) via a Williamson ether synthesis to yield a nonionic surfactant with a critical micelle concentration of **1.2 × 10⁻⁴ M** in deionized water at **25 °C** (determined by Wilhelmy plate tensiometry, **DIN EN 14370:2004**). The adjuvant is blended into an emulsifiable concentrate (EC) formulation at **8–12% w/w**, together with **20% w/w** active ingredient and **68–72%** aromatic hydrocarbon solvent. The batch is emulsified at **6000 rpm** for **15 minutes** using a Silverson L5M-A high-shear rotor-stator mixer equipped with a fine emulsor screen; the resulting emulsion must exhibit a droplet size **Dv90 ≤ 3.5 µm** when diluted in **342 ppm** standard hard water under **CIPAC MT 36.2**. Compliance is audited against **FAO Manual on development and use of specifications for pesticides, March 2022 revision**, specifically Section **5.3.3** concerning non-marked adjuvants, and the EC storage stability must pass the **CIPAC MT 46.1** accelerated test at **54 ± 2 °C** for **14 days** with phase separation below **2% v/v**. The terminal products are commercial soybean rust control packages combining a QoI fungicide with the thiazole-based penetration modifier, which reduces the required per-hectare active ingredient rate from **100 g a.i./ha** to **72 g a.i./ha** without a statistical loss of efficacy in field trials across **12** Brazilian growing sites.2-Methylthiazole Monomers in Chemically Amplified 193nm Resist SystemsThe electron-deficient nature of the 2-methylthiazole ring has been exploited in next-generation photoresists designed for ArF immersion lithography. The chloromethyl derivative is used to functionalize poly(4-hydroxystyrene)-co-poly(tert-butyl acrylate) (PHS-tBA) matrices by esterification of a fraction of the hydroxystyrene units; the resulting polymer incorporates a pendant thiazole group that increases the absorbance at **193 nm** from a baseline **K-value of 0.08 µm⁻¹** to **0.32 µm⁻¹**, thereby improving the dissolution inhibition contrast in tetramethylammonium hydroxide developers at **0.26 N**. In a typical formulation, the thiazole-grafted polymer constitutes **6–9 wt%** of the total solids dissolved in propylene glycol monomethyl ether acetate (PGMEA), with the balance comprising a triphenylsulfonium nonaflate photoacid generator at **4–6 wt%** and a tert-butoxycarbonyl-protected quencher at **0.8–1.2 wt%**. Coatings are spin-cast on **300 mm** prime silicon wafers with a bottom anti-reflective coating ( **Brewer Science ARC29A** ) at **1500 rpm** to obtain a dried film thickness of **110 ± 2 nm**, followed by a post-apply bake at **110 °C** for **90 seconds** on a Tokyo Electron ACT12 track. After exposure with an ASML Twinscan XT:1900i scanner at a dose of **28–32 mJ/cm²** and post-exposure bake at **115 °C**, the development process yields **45 nm** dense lines with a line-width roughness of **3.1 nm (3σ)** measured via CD-SEM. The material is evaluated against **SEMI S7-0920** (Environmental, Health, and Safety Guideline for Semiconductor Manufacturing Equipment) and the resist components are screened for heavy metals under **RoHS Directive 2011/65/EU** Annex IV exemption **34**, with lead and cadmium concentrations not exceeding **100 ppm** and **20 ppm** respectively by ICP-MS.Enhancing Anodic Stripping Voltammetry Sensors via Covalent Attachment to Screen-Printed Carbon ElectrodesA divergent application route involves immobilizing the thiazole heterocycle onto disposable electrochemical sensors for the trace determination of cadmium(II) and lead(II) in industrial wastewater. The sensor fabrication begins with a carbon ink formulated by mixing commercial graphite powder ( **< 20 µm** particle size, TIMCAL Timrex KS6) with a vinyl chloride-vinyl acetate copolymer binder in isophorone at a **70:15:15** weight ratio, to which 5-(chloromethyl)-2-methylthiazole is directly added at **3.5% w/w** of the ink solids. The ink is passed through a triple-roll mill with a gap setting descending from **40 µm** to **5 µm** until the fineness of grind reaches **< 8 µm** per **ISO 1524:2020**. Screen-printing onto polyethylene terephthalate substrates using a **230-mesh** stainless steel screen yields electrodes with an active geometric area of **12.6 mm²**; the chloromethyl anchor reacts spontaneously with hydroxyl groups on the carbon surface during thermal curing at **60 °C** for **45 minutes** in a forced-air oven. The analytical protocol, accredited under **ISO/IEC 17025:2017**, applies square-wave anodic stripping voltammetry with a deposition potential of **−1.2 V (vs. Ag/AgCl)** for **300 seconds**, stripping in a **0.1 M** acetate buffer (pH **4.5**). The thiazole-modified electrode lowers the limit of detection for Pb(II) from **1.8 µg/L** to **0.3 µg/L** compared to the unmodified sensor, with inter-electrode relative standard deviation of **4.7%** (n= **15** ), and each device is validated against the **US EPA SW-846 Method 3130** acceptance criteria for aqueous metal analysis. The end-use format is a single-use, three-electrode strip deployed in portable potentiostats at metal-plating facility discharge outfalls.
Oligomeric Quinoidal Thiazole for Near-Infrared Absorbing DyesIn the synthesis of croconium and squarylium dyes for security inks and optical data storage, the thiazole precursor is converted to a quaternized salt that undergoes Knoevenagel condensation. Initially, 5-(chloromethyl)-2-methylthiazole is heated with an equimolar amount of 2,6-di-tert-butyl-4-methylpyridine (a non-nucleophilic base) and **0.50 equivalents** of croconic acid in a solvent mixture of n-butanol and toluene ( **2:1 v/v** ) under a Dean-Stark trap at **120 °C** for **6 hours**. After solvent stripping, the crude oligomeric dye is precipitated into diethyl ether, collected, and washed until the filtrate conductivity falls below **10 µS/cm**. The purified material exhibits a molar extinction coefficient of **5.8 × 10⁴ L·mol⁻¹·cm⁻¹** at **802 nm** in chloroform, meeting the spectral requirement for ISO 1831-compliant optical character recognition ink. Formulation of the ready-to-print ink incorporates the dye at **2.0–2.5 wt%** in methyl ethyl ketone with a polyvinyl butyral binder ( **Mw 50,000–70,000** ) at **8 wt%** and dibutyl phthalate plasticizer at **2 wt%**. Printing trials are performed on a narrow-web flexographic press using a **120 line/cm** anilox roll; the printed dots on polypropylene must yield a print contrast signal exceeding **0.85** when read by a near-infrared camera under **860 nm** LED illumination, per **ISO/TR 19782:2011**. The terminal deliverable is a covert anti-counterfeiting label for pharmaceutical secondary packaging, requiring compliance with **US FDA 21 CFR 175.105** for indirect food additives when the labels are applied to unit-dose blister foils. A documented operational boundary is the sensitivity of the croconate dye to singlet oxygen; the printing must be conducted under amber safelight with ambient oxygen levels below **1000 ppm**, otherwise fading exceeds **15%** within **72 hours** of UV-A exposure at **0.68 W/m²**. |
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5-(Chloromethyl)-2-methylthiazole (CAS 37847-34-6, empirical formula C5H6ClNS, molecular weight 147.62 g mol-1) is a liquid-phase heteroaromatic alkylating agent produced by photochlorination or radical-mediated chlorination of 2,5-dimethylthiazole. The molecule presents a distal chloromethyl group at the thiazole C-5 position, imparting electrophilic reactivity controlled by the electron-withdrawing character of the sulfur–nitrogen heterocycle. Commercial material is typically supplied as a pale-yellow to amber oil with a boiling point of 92–95 °C at 15 mmHg and a density of 1.226 g cm-3 at 20 °C. Purity by gas chromatography (area normalization, DB-5 column, 30 m × 0.32 mm, film 0.25 µm) exceeds 97.0 %, with the primary impurity being the dichloromethyl congener controlled at ≤1.2 %. Free acidity, expressed as HCl, is maintained below 0.15 % to limit autogenous degradation during transit. This intermediate serves as a key building block in the synthesis of thiazole-bearing fungicides, pharmaceutical active pharmaceutical ingredients (APIs), and curing co-agents for specialized elastomers, where the chlorine atom acts as a leaving group in nucleophilic substitution, N-alkylation, and metal-catalysed cross-coupling reactions. The discussion below dissects the specific handling envelope, comparative reactivity, and end-use integration gaps that differentiate this chloromethyl derivative from its brominated and positional-isomer counterparts.
Stability monitoring on a pilot-plant scale (borosilicate glass-lined vessels, 500 L capacity, subsurface nitrogen sparge) indicates that 5-(chloromethyl)-2-methylthiazole undergoes progressive discoloration and dimerization when held above 40 °C for periods exceeding 72 h. Differential scanning calorimetry (DSC) at a ramp rate of 5 K min-1 reveals an exotherm onset at 168 °C (ΔH −640 J g-1) attributable to self-alkylation polymerization. For this reason, bulk storage under nitrogen blanket with active chilling to 2–8 °C is mandatory in warehouses where ambient summer temperatures exceed 30 °C. The product is hygroscopic; water absorption above 0.08 wt% accelerates hydrolysis, liberating HCl that catalyzes further decomposition. Metered transfer to synthesis suites employs magnetically coupled gear pumps with perfluoroelastomer static seals (FFKM, Kalrez® compound 4079), as ethylene-propylene diene monomer (EPDM) seals exhibit swelling of 12–15 % volume increase within 48 h exposure. In continuous-flow alkylation campaigns, a Coriolis mass flow meter (Endress+Hauser Proline Promass F) provides dosing precision of ±0.15 % of setpoint, critical where stoichiometric imbalance induces bis-alkylated byproduct formation.
Direct head-to-head comparison of 5-(chloromethyl)-2-methylthiazole with its 5-(bromomethyl) counterpart under identical conditions (acetonitrile, 50 mM substrate, 2.0 eq sodium phenolate, 40 °C) yields a second-order rate constant ratio kBr/kCl of 11:1, measured by LC–UV monitoring of phenol consumption. The brominated derivative reaches 95 % conversion in 2.1 h, whereas the chloromethyl compound requires 17 h. Despite the slower kinetics, the chlorine leaving group offers a distinct process advantage in multistep sequences where chemoselectivity must be preserved: the chloromethyl analogue tolerates a wider window of competing nucleophiles (e.g., secondary amides, sulfonamide anions) without premature alkylation, allowing sequential bond formation without protecting group manipulation. Furthermore, the bromomethyl compound generates potent lachrymatory and vesicant aerosols during drum charging, necessitating closed-transfer dry-break coupling (Stäubli DLS) and face-velocity containment ≥0.5 m s-1 on downflow booths. The chloromethyl derivative, while still a sensitizer, poses manageable vapour pressure (0.12 mmHg at 25 °C versus 0.03 mmHg for the bromo compound, but the latter’s higher intrinsic toxicity dominates the risk profile). This practical distinction frequently tips the manufacturing decision toward the chlorinated intermediate when campaign durations require multiple drum changes.
The compound is typically isolated by fractional vacuum distillation with a toluene flush to displace dichloromethane or chloroform origins. If the concentration of carryover toluene or hexane exceeds 0.5 wt% (determined by headspace GC-FID per USP ⟨467⟩ Procedure A), downstream N-alkylation of pyrimidine-dione scaffolds exhibits variable induction periods, causing erratic heat release on scale-up. A validated process specification for pharmaceutical coupling therefore mandates residual volatiles below 0.3 % (summed over all Class 2 solvents per ICH Q3C). In one campaign producing a thiazole-substituted triazolone antifungal (structural analog of prothioconazole), batch records indicate that a solvent excursion to 0.7 % toluene resulted in a 14-minute delay in reaction initiation, followed by a bimodal exotherm that exceeded jacket cooling capacity (−25 °C brine, 8.5 kW removal) and triggered a safety interlock. Root-cause analysis traced the excursion to an incomplete distillate cut during product fractionation across a wiped-film evaporator (UIC KDL 5, jacket temperature 110 °C, pressure 3 mbar). This highlights the practical engineering boundary: the separation between the product boiling point and the tail-end toluene fraction narrows to less than 15 °C at reduced pressure, demanding a reflux ratio ≥4:1 on packed columns dimensioned for structured packing (Sulzer Mellapak 500.X).
Agricultural fungicide manufacturing, specifically the production of thifluzamide and related 2-methylthiazole-5-carboxanilides, consumes the largest industrial volume of 5-(chloromethyl)-2-methylthiazole. In a representative two-stage telescoped process, the chloromethyl compound is first treated with sodium cyanide in aqueous DMF (50 °C, 4 h) to generate the nitrile intermediate, which is subsequently hydrolyzed to the corresponding carboxylic acid under acidic conditions. The critical quality attribute is the absence of ring-chlorinated impurities that arise when free-radical chlorination overshoots at the 2-methyl position; such impurities are carried into the final product, elevating the AOX (adsorbable organic halide) content of the technical fungicide. A dedicated production campaign at a multipurpose agrochemical facility (ISO 9001:2015 certified, operating under EPA Pesticide Registration Notice 98-2) established a release limit of ≤0.4 area% for 2-(chloromethyl)-5-methylthiazole isomer by GC. The economics of this route are benchmarked against the alternative o-dichlorobenzene-phosphorus pentachloride chlorination of 2,5-dimethylthiazole; the photochlorination route generating the specified 5-chloromethyl isomer delivers an atom economy advantage of 22 %, calculated as (MWproduct/(MWstarting thiazole + MWCl2)) × 100.
Beyond its role as a synthesis intermediate, the compound can be chemically grafted onto polymer backbones to serve as a latent sulfur-donor precursor in the vulcanization of hydrogenated nitrile butadiene rubber (HNBR) and fluorocarbon elastomers (FKM). When the chloromethyl group is utilized to anchor the thiazole ring onto a silica filler surface via a quaternization reaction with γ-mercaptopropyltrimethoxysilane (Silquest A-189), the resulting functionalized filler imparts scorch delay without sacrificing crosslink density. In compounding trials on a laboratory two-roll mill (200 mm × 400 mm, friction ratio 1:1.2, roll temperature 45 °C), an HNBR compound (Therban 3446, 100 phr) containing carbon black N550 (40 phr), zinc oxide (5 phr), stearic acid (1 phr), and dicumyl peroxide (4 phr) was modified with 2.5 phr of the silane-grafted 5-(chloromethyl)-2-methylthiazole adduct. Curemetry at 170 °C (Monsanto MDR 2000, arc 0.5°) documented a scorch time ts2 increase from 1.1 min to 2.8 min while the maximum torque MH rose from 18.2 dNm to 22.7 dNm, indicating enhanced network formation.
| Property | Control (unmodified silica) | 2.5 phr Thiazole-Silica | 5.0 phr Thiazole-Silica |
|---|---|---|---|
| Tensile strength (ASTM D412, die C) | 18.2 MPa | 23.5 MPa | 24.1 MPa |
| Elongation at break | 420 % | 385 % | 340 % |
| Modulus at 100 % strain | 2.8 MPa | 4.1 MPa | 5.3 MPa |
| Crosslink density (by equilibrium swelling, ASTM D471) | 4.2×10-5 mol cm-3 | 6.8×10-5 mol cm-3 | 8.3×10-5 mol cm-3 |
The grafted chloromethyl thiazole must be strictly anhydrous during silanization; moisture above 0.05 % promotes premature hydrolysis of the silane’s trimethoxy groups, collapsing the coupling efficiency to less than 40 % as detected by X-ray photoelectron spectroscopy (XPS) Si 2p peak integration. Post-cure aging in ASTM #3 oil at 150 °C for 168 h confirmed retention of tensile strength above 90 %, validating the thiazole bridge’s resistance to hot-oil extraction, a point of failure for simpler ester-based coupling architectures. The incompatibility of this chloromethyl-functionalized filler with amine-based antioxidants (e.g., alkylated diphenylamines) is notable: co-incorporation resulted in a 35 % reduction in MH, attributed to nucleophilic quenching of the chloromethyl site by the amine, forming a non-reactive quaternary ammonium pendant that interferes with the sulfur crosslinking cascade.
| Parameter | Pharma-Grade | Industrial-Grade |
|---|---|---|
| Assay (GC, area%) | ≥ 99.0 % | ≥ 97.0 % |
| Isomeric impurity (2-chloromethyl-5-methylthiazole) | ≤ 0.15 % | ≤ 0.60 % |
| Water (Karl Fischer, ASTM E203) | ≤ 0.05 % | ≤ 0.10 % |
| Heavy metals (as Pb, USP ⟨231⟩) | ≤ 10 ppm | Not routinely tested |
| Residual Pd (in case of cross-coupling feedstock) | ≤ 5 ppm (ICP-MS) | Report only |
| Bacterial endotoxins (LAL) | ≤ 0.05 EU mg-1 | Not applicable |
Differences between 5-(chloromethyl)-2-methylthiazole and its closest structural relatives are operationally meaningful. The 2-methyl substituent exerts a steric and electronic influence that moderates the reactivity of the chloromethyl group compared to 5-(chloromethyl)thiazole (lacking the 2-methyl). In the unmethylated variant, the ring is slightly more electron-deficient, accelerating nucleophilic displacement, but also increasing sensitivity to aqueous hydrolysis during workup; a quench step at pH 8 with 0.5 M phosphate buffer showed 18 % hydrolysis of the 2-H derivative within 30 min, whereas the 2-methyl analog hydrolyzed only 3 % under identical conditions. In contrast, 2-(chloromethyl)benzothiazole, while superficially similar, cannot access the same conformational profile for active-site binding in fungicidal target proteins—molecular docking studies of the succinate dehydrogenase (SDH) complex indicate that the planar benzothiazole system introduces a 12° dihedral angle mismatch with the enzyme’s ubiquinone-binding pocket, reducing inhibition potency tenfold. Thus, the thiazole core with a sole 2-methyl group occupies a specific reactivity–bioactivity envelope distinct from both smaller-ring heterocycles and benzo-fused derivatives, making 5-(chloromethyl)-2-methylthiazole a uniquely positioned intermediate for modern agrochemical and pharmaceutical discovery programs.
Operating boundaries extend to effluent treatment. Waste streams containing hydrolyzed thiazole derivatives and chloride salts must undergo oxidative treatment (Fenton’s reagent, H2O2:FeSO4 molar ratio 10:1, pH 3, 60 min) to mineralize the thiazole ring before discharge to biological wastewater treatment; direct exposure to activated sludge has been observed in pilot tests to inhibit nitrification at concentrations as low as 25 mg L-1. Drum emptying and line flushing protocol demands nitrogen-padded pigging systems to recover heel volumes exceeding 2 % of the drum capacity, thereby minimizing volatile organic emission and operator exposure below the permissible exposure limit of 0.5 ppm (eight-hour time-weighted average, as per analogous alkylating agent guidance). These integrated handling, specification, and disposal constraints define the product’s industrial life cycle far beyond the simple molecular descriptor, framing the chloromethyl thiazole as a tool suited to high-value, tightly controlled synthetic transformations rather than untargeted bulk alkylation applications.
