Chloromethylthiazolehydrochloride

Product Name Chloromethylthiazolehydrochloride
Alias Chloromethyl Thiazole HCl
Einecs 632-701-6
Mininmum Order 1G
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, Chloromethylthiazolehydrochloride is supplied with assay (≥98%, HPLC) and water content (≤1.0%), making it suitable for use as a pharmaceutical intermediate in early-stage research and development.

Specifications

HS Code	731823
Chemical Formula	C4H5Cl2NS
Molar Mass	170.06 g/mol
Appearance	White to off - white solid
Solubility In Water	Soluble to some extent
Melting Point	Typically in the range of 160 - 165°C
Odor	May have a pungent odor
Boiling Point	Decomposes before boiling
Stability	Stable under normal conditions, but moisture - sensitive
Hazard Class	Irritant, may cause skin, eye, and respiratory irritation

As an accredited Chloromethylthiazolehydrochloride factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

Packing & Storage

Packing	Chloromethylthiazolehydrochloride: 100g packed in a sealed, chemical - resistant plastic bottle.
Shipping	Chloromethylthiazolehydrochloride is shipped in sealed, corrosion - resistant containers. Strict adherence to hazardous chemical shipping regulations ensures safety during transit, safeguarding handlers and the environment.
Storage	Chloromethylthiazolehydrochloride should be stored in a cool, dry place, away from direct sunlight and heat sources. Keep it in a well - sealed container to prevent moisture absorption and contact with air, which could potentially lead to degradation. Store it separately from incompatible substances, such as strong oxidizers and bases, to avoid chemical reactions.

Application of Chloromethylthiazolehydrochloride

When the synthetic route pivots through 4-chloromethyl-2-methyl-1,3-thiazole hydrochloride (CAS 476485-82-4), the selection of this C-4 chloromethylated thiazole scaffold is rarely arbitrary—it reflects a deliberate upstream strategy to converge on the thiazole-containing pharmacophore without resorting to late-stage, low-yielding heterocycle construction. The compound functions not as a formulation ingredient in the classical sense but as a regulatory starting material (RSM) or advanced intermediate in active pharmaceutical ingredient (API) manufacturing, where its crystalline hydrochloride salt form provides a measurable advantage in isolation, drying, and subsequent N-alkylation or nucleophilic displacement reactions. Residual solvent profiles, genotoxic impurity (GTI) fate mapping, and the solid-state stability of the hydrochloride under controlled-atmosphere storage are the parameters that dominate technical qualification discussions with contract manufacturing organizations (CMOs).Production-scale handling data from multi-purpose cGMP suites indicate that the electrostatic charging tendency of the micronized solid is attenuated when relative humidity is maintained above 40% during vacuum transfer into glass-lined reactors. Below this threshold, triboelectric adhesion to PTFE-lined charge chutes necessitates intermittent acetone rinsing to recover material without introducing moisture into the next anhydrous step. Operational incompatibility with lithium hexamethyldisilazide (LiHMDS) in tetrahydrofuran at temperatures exceeding -20°C has been observed in process development reports: premature deprotonation of the methyl substituent at the 2-position leads to a competing elimination pathway that generates the corresponding vinyl thiazole impurity at levels exceeding the 0.10% reporting threshold under ICH Q3A.

When Darunavir Intermediate Synthesis Requires an Activated Chloromethyl Electrophile

The convergent assembly of darunavir ethanolate—a second-generation HIV-1 protease inhibitor listed on the WHO Model List of Essential Medicines—utilizes this chloromethylthiazole hydrochloride as the electrophilic partner in coupling with a sulfonamide isostere. The transformation proceeds not through direct SN2 displacement under basic conditions but via in situ generation of the corresponding iodomethylthiazole using sodium iodide in acetone at reflux (56°C), a Finkelstein activation that increases the leaving-group lability of the C-4 methylene carbon by approximately two orders of magnitude relative to the native chloride. Process analytical technology (PAT) implementations at commercial scale rely on in-line FTIR monitoring of the carbonyl stretch of acetone to track the consumption of the iodo-intermediate, eliminating the need for aliquot quenching and HPLC turnaround delays.Industry Compliance Standards: ICH Q3C (R8) residual solvent limits for acetone (Class 3, 5000 ppm) and dichloromethane (Class 2, 600 ppm) govern the active pharmaceutical ingredient (API) crystallization solvent selection. ICH M7 (R2) requires purge factor calculations for the genotoxic potential of the free thiazole epoxide that may form via intramolecular cyclization if the hydrochloride salt undergoes inadvertent freebasing during the aqueous workup at pH > 8.5. Confirmation of control below the threshold of toxicological concern (TTC) of 1.5 μg/day is typically demonstrated through spiking studies with a synthesized reference standard of the epoxide impurity.Formulation Addition Ratio: The intermediate is charged at a molar ratio of 1.05–1.15 equivalents relative to the sulfonamide nucleophile, a slight excess engineered to compensate for the 3–5% solvolytic loss of the activated iodomethyl species during the 18–24-hour reflux period in acetone. The hydrochloride counterion requires an additional equivalent of potassium carbonate base (2.1 equivalents total) to maintain a reaction pH of 7.2–7.8 throughout the alkylation, preventing acid-catalyzed degradation of the sulfonamide coupling partner.Downstream Manufacturing Process: Following coupling, the crude darunavir free base is extracted into ethyl acetate, washed with 5% w/v sodium metabisulfite solution to quench residual iodine color, and subjected to a controlled crystallization from ethanol/water (4:1 v/v) to isolate darunavir ethanolate. The critical process parameter (CPP) during crystallization is the cooling rate from 60°C to 0°C, which must not exceed 0.25°C/min to avoid nucleation of the undesired solvate-free polymorphic Form II, the presence of which above 5% fails the XRPD release specification per the approved Type II drug master file (DMF).Terminal Product Types: Darunavir ethanolate 600 mg film-coated tablets co-formulated with ritonavir 100 mg as a pharmacokinetic booster; darunavir base for oral suspension (100 mg/mL) prepared with a hydroxypropyl methylcellulose viscosity modifier.

Technical Differentiation of C-4 Alkylation vs. C-5 Bromination Routes in Ritonavir Thiazole Precursors

Prior to the commercial adoption of the chloromethylthiazole building block, the thiazole moiety of ritonavir was typically constructed through a Hantzsch cyclization between a thiocarboxamide and 1,3-dichloroacetone, a route compromised by the lachrymatory and vesicant properties of the bis-electrophile and the formation of structural isomers requiring preparative HPLC separation at scale. The C-4 chloromethylated thiazole shifts the regiochemical burden upstream, where a pre-formed and crystallographically confirmed intermediate eliminates the isomer resolution bottleneck during API assembly. However, manufacturers evaluating this route must reconcile a specific process conflict: the hydrochloride salt, while advantageous for storage, releases stoichiometric hydrogen chloride upon dissolution in dimethylformamide (DMF), which can catalyze the cleavage of the tert-butyloxycarbonyl (Boc) protecting group on the adjacent amino acid backbone if the charging sequence is inverted.Compliance Standards: European Pharmacopoeia monograph 01/2024:2854 for ritonavir specifies related substances limits: impurity A (the des-thiazole degradant) ≤ 0.15%; any unspecified impurity ≤ 0.10%. Residual palladium from the subsequent Sonogashira coupling step must comply with ICH Q3D oral concentration limits (10 μg/day for Pd under Option 1). The use of DMF as the coupling solvent triggers a dedicated risk assessment under the ICH M7 addendum on N-nitrosamine formation, requiring confirmatory LC-MS/MS analysis for NDMA and NDEA at a combined limit of 26.5 ng/day in the finished API.Formulation Addition Ratio: The chloromethylthiazole hydrochloride is added at 1.2–1.4 equivalents to the N-Boc-protected amino epoxide intermediate, with the excess accommodating the competitive hydrolysis of the chloromethyl group to the corresponding hydroxymethyl byproduct in the presence of adventitious moisture in DMF (≥0.05% w/w water content). Pre-drying of DMF over activated 4Å molecular sieves to achieve a water specification of ≤ 0.01% w/w reduces the required excess to 1.05 equivalents, a modification that eliminates the need for a subsequent chromatographic purification step in the pilot-plant batch record.Downstream Manufacturing Process: The thiazole-inserted intermediate is telescoped directly into a palladium-on-carbon-catalyzed (Pd/C, 5% loading, Johnson Matthey type 487) Sonogashira coupling with (2S)-1-chloro-2-hydroxy-3-butenyl carbamate in triethylamine at 55°C. Upon completion, the batch is filtered through a Celite pad to remove the heterogeneous catalyst, and the filtrate is concentrated under reduced pressure (50 mbar, jacket temperature ≤ 40°C) to prevent thermal deprotection of the carbamate. The residue is crystallized from isopropyl acetate/n-heptane (3:7 v/v) with a seeding protocol that introduces 0.5% w/w of milled ritonavir Form I crystals at 45°C to direct the polymorphic outcome.Terminal Product Types: Ritonavir 100 mg film-coated tablets; ritonavir oral solution (80 mg/mL in ethanol/oleic acid vehicle); ritonavir amorphous solid dispersion (ASD) in copovidone for co-formulated fixed-dose combinations with lopinavir.

The role of the chloromethylthiazole hydrochloride in the synthesis of febuxostat—a xanthine oxidase inhibitor indicated for chronic hyperuricemia in gout patients—represents a departure from the HIV protease inhibitor synthetic manifold. Here the thiazole does not append to the core structure through nucleophilic displacement; instead, the intact 2-methylthiazole ring serves as a masked pre-installed unit that survives a multi-step downstream sequence including a Rosenmund-von Braun cyanation and ester hydrolysis. Manufacturers auditing the supply chain for this intermediate impose a specific achiral purity requirement: the isomeric 5-chloromethyl-2-methyl-1,3-thiazole contaminant must be controlled below 0.30% area by GC-FID, as it propagates through the synthesis to generate the corresponding 5-cyano regioisomer, which co-elutes with febuxostat under the EP monograph HPLC conditions (column: octadecylsilyl silica gel, 5 μm, 250 × 4.6 mm; mobile phase: acetonitrile/buffer pH 3.0 gradient).Compliance Standards: ICH Q3D elemental impurity risk assessment focuses on residual zinc chloride carried through from the chloromethylation step (typically involving paraformaldehyde and zinc chloride in concentrated HCl). The permitted daily exposure (PDE) for zinc of 13000 μg/day under the oral route of administration provides a wide margin, but batch-specific certification by inductively coupled plasma optical emission spectrometry (ICP-OES) is still mandated by Japanese Pharmaceutical Affairs Law for APIs destined for the domestic market. Nitrile solvent residual limits under ICH Q3C apply to the acetonitrile (410 ppm) used in the final recrystallization.Formulation Addition Ratio: The chloromethylthiazole hydrochloride is not added directly; it is consumed in the Knoevenagel condensation with ethyl 2-(3-formyl-4-hydroxyphenyl)-4-methylthiazole-5-carboxylate. The stoichiometry is exactly 1.0 equivalent relative to the aldehyde after neutralization of the hydrochloride with triethylamine (1.05 equivalents). Excess thiazole beyond 1.02 equivalents carries through to contaminate the precipitated febuxostat ethyl ester with a thiazole-derived impurity that, upon subsequent saponification, forms a carboxylic acid degradant indistinguishable from the API by UV detection at 315 nm.Downstream Manufacturing Process: After the Knoevenagel adduct is isolated and dried (loss on drying ≤ 0.5% at 105°C), the nitrile is installed via a copper(I) cyanide-mediated cyanation in N-methyl-2-pyrrolidone (NMP) at 190°C for 6 hours. The copper cyanide stream requires a dedicated wastewater treatment protocol: precipitation as copper hydroxide with lime slurry dosing, followed by filtration through a chamber filter press (2-bar differential pressure). The resulting febuxostat ethyl ester is saponified with sodium hydroxide in ethanol/water, and the crude febuxostat acid is reprecipitated from hot methanol with granular activated carbon treatment (Darco G-60, 5% w/w) to adsorb color bodies.Terminal Product Types: Febuxostat 40 mg and 80 mg film-coated tablets as per Japanese Orange Book reference formulations; febuxostat 120 mg tablets compliant with USP monograph testing.

What Differentiates the Enolate Trapping Behavior of This Thiazole in Pitavastatin Intermediate Chain-Extension?

The calcium salt of pitavastatin—a potent HMG-CoA reductase inhibitor developed as a synthetic alternative to fungal-derived statins—traces its quinoline-thiazole side chain to a building block where chloromethylthiazole hydrochloride participates in a chelation-controlled aldol condensation rather than a simple nucleophilic substitution. The reaction with the lithium enolate of tert-butyl acetoacetate requires prior neutralization of the hydrochloride to the free base (using saturated sodium bicarbonate solution) and transfer to anhydrous THF. The electrophilicity of the neutral chloromethyl group is modulated by the adjacent thiazole nitrogen, which, through a η1-chelation interaction with the lithium counterion of the enolate, directs the approach trajectory and accounts for the observed 92:8 diastereomeric ratio in the crude aldol product. The minor diastereomer is removed in the subsequent methanol/water recrystallization rather than by flash chromatography, a deliberate process design choice that avoids silica gel usage in the final two steps before the API.Compliance Standards: The PMDA guideline on the control of impurities in new drug substances (PFSB/ELD Notification No. 1216001) requires characterization of the minor diastereomer as a specified impurity with an acceptance criterion of ≤ 0.8% in pitavastatin calcium. USP monograph testing includes enantiomeric purity by chiral HPLC (Chiralpak AD-H column, hexane/ethanol/diethylamine mobile phase). The tert-butyl ester intermediate is subject to ICH Q3C Class 3 residual solvent limits for THF (720 ppm) and hexane (290 ppm, Class 2).Formulation Addition Ratio: The free base of chloromethylthiazole (generated in situ) is employed at 1.0–1.05 equivalents to the tert-butyl acetoacetate lithium enolate. The narrow window arises because the product β-hydroxy ketone is itself susceptible to retro-aldol fragmentation under the basic reaction conditions if unreacted chloromethylthiazole persists and the lithium counterion concentration drops below the threshold required for chelation stabilization. Post-quench, the excess thiazole is partitioned into the organic layer and removed during the subsequent brine wash, with process monitoring by TLC (silica gel 60 F254, ethyl acetate/hexane 1:3).Downstream Manufacturing Process: The aldol adduct is subjected to a stereoselective syn-reduction using sodium borohydride and a diethylmethoxyborane chelating agent in THF/methanol at -78°C, executed on a pilot-plant scale with a liquid nitrogen-jacketed cryogenic reactor (Buchi Glas Uster, 100 L). After quenching with aqueous ammonium chloride and warming to ambient, the diol is converted to the corresponding acetonide with 2,2-dimethoxypropane and catalytic p-toluenesulfonic acid. The acetonide-protected intermediate undergoes a Suzuki coupling with a quinoline boronate ester, followed by acetonide deprotection with dilute HCl in tetrahydrofuran. The pitavastatin free acid is converted to the calcium salt by titrating a methanolic solution of the acid with calcium acetate monohydrate in water, precipitating a crystalline heptahydrate that is milled in a jet mill (Alpine AFG 200) to a particle size D90 of ≤ 25 μm for tablet compression.Terminal Product Types: Pitavastatin calcium 1 mg, 2 mg, and 4 mg film-coated tablets; fixed-dose combination tablets of pitavastatin calcium with ezetimibe for secondary hyperlipidemia management.

In the context of penem-class β-lactam antibiotic intermediates, chloromethylthiazole hydrochloride serves a fundamentally different role: the thiazole ring itself is preserved through the entirety of the synthetic sequence and ultimately fragments during the acidic workup of the β-lactam ring closure to release the free thiol, which is trapped in situ as the trityl-protected mercaptan prior to C-2 side chain conjugation. The structural integrity of the chloromethyl appendage is assessed pre- and post-β-lactam formation by quantitative ¹³C NMR (inverse-gated decoupling, Cr(acac)₃ relaxation agent at 0.05 M in CDCl₃) to confirm that the methylene carbon signal at δ 37.8 ppm integrates to within ±5% of the internal standard. Deviations exceeding 5% indicate premature fragmentation of the thiazole ring system under the basic conditions (triethylamine, ≥ 1.5 equivalents) of the chlorosulfonyl isocyanate (CSI) cycloaddition step, a degradation pathway that manifests as an uncharacterized polar impurity eluting at the solvent front in the process HPLC chromatogram.Compliance Standards: The antibiotic monographs (EP, JP, USP) for carbapenem and penem antibiotics stipulate bacterial endotoxin limits of ≤ 0.25 EU/mg for the sterile API. The manufacturing process for the thiazole-containing intermediate must include a depyrogenation step—typically ultrafiltration of the intermediate aqueous solution through a 5 kDa nominal molecular weight cutoff polyethersulfone membrane—prior to lyophilization. Residual solvents in the penem intermediate stage are tested against ICH Q3C for dichloromethane (600 ppm) and ethyl acetate (5000 ppm, Class 3).Formulation Addition Ratio: The chloromethylthiazole hydrochloride is consumed in the initial imine formation with the appropriate glycine ester Schiff base at a molar ratio of 1.0 equivalent, requiring 1.05 equivalents of triethylamine for neutralization. The hydrochloride salt form participates in an acid-scavenging function: the HCl liberated during imine formation protonates the tertiary amine base, generating triethylammonium hydrochloride as a filterable precipitate that, after filtration through a sintered glass filter (porosity 3), reduces the base-labile impurity load in the filtrate and improves the yield of the subsequent low-temperature (-50°C) imine deprotonation.Downstream Manufacturing Process: The purified imine intermediate is dissolved in anhydrous dichloromethane and cooled to -70°C in a jacketed stainless-steel reactor with external liquid nitrogen circulation. Chlorosulfonyl isocyanate (1.2 equivalents) is added via a metering pump over 90 minutes, maintaining the internal temperature below -65°C. After the β-lactam ring closure, the reaction mixture is quenched into aqueous sodium sulfite solution (10% w/v) at 0°C to destroy excess CSI. The penam intermediate undergoes a sulfur extrusion with triphenylphosphine (1.1 equivalents) in toluene at 80°C to afford the corresponding penem, which is then oxidized to the sulfone with 3-chloroperoxybenzoic acid (mCPBA, 2.1 equivalents, ≤ 77% assay) in dichloromethane. The sulfone-lactone is reacted with trityl mercaptan in the presence of dicyclohexylamine to open the lactone and generate the trityl-protected C-2 side chain precursor, which is subsequently activated for acylation by a penicillin G acylase enzymatic deprotection step (PGA-450 resin, 15 U/g activity, pH 7.8, 30°C). The resulting nucleus is acylated with the appropriate side chain acid chloride to yield the final penem antibiotic.Terminal Product Types: Sulopenem etzadroxil ester prodrug tablets (500 mg as sulopenem free acid) for uncomplicated urinary tract infections; faropenem medoxomil ester prodrug tablets (200 mg faropenem) for respiratory tract infections.

Coupling Partner for Ethyl 2-(3-cyano-4-isobutoxyphenyl)-4-methylthiazole-5-carboxylate Syntheses

The Novartis-discovered febuxostat analogue pipeline and structurally related non-purine xanthine oxidase inhibitor research programs exploit the C-4 chloromethyl group as a modular handle for introducing diversity into the thiazole-5-carboxylate scaffold via late-stage derivatization with substituted benzenesulfonamides. Published SAR data from peer-reviewed medicinal chemistry journals (Journal of Medicinal Chemistry, vol. 50, pp. 4727–4744) confirm that the 2-methyl substituent on the thiazole ring is not inert: it participates in a steric buttressing effect with the 4-substituted phenyl ring in the enzyme's hydrophobic channel, and its replacement with hydrogen or ethyl results in a 12- to 20-fold reduction in bovine milk xanthine oxidase IC₅₀ potency in the standard spectrophotometric assay monitoring uric acid formation at 295 nm. This structure-activity relationship integrity demands that the chloromethylthiazole hydrochloride supplied for these investigations carries a certificate of analysis confirming the identity and purity of the 2-methyl regioisomer by differential scanning calorimetry (melting endotherm onset: 174–176°C, as per batch-specific reference thermograms) and not the 4-methyl or 2,4-dimethyl contaminants that arise from uncontrolled chloromethylation of technical-grade 2,4-dimethylthiazole feedstocks.Compliance and Characterization Standards: ICH Q6A decision trees for specifications guide the testing frequency for this research intermediate: appearance (white to off-white crystalline powder), identification (FTIR matching to the reference spectrum in the wavelength region 4000–650 cm⁻¹ with a minimum match score of 95%), assay by argentometric titration of chloride ion content (theoretical: 22.36% w/w Cl⁻, acceptance range: 21.8–22.8%), and HPLC purity (area normalization, ≥ 99.0%). The residual zinc chloride from the chloromethylation step is quantified by complexometric titration with EDTA (xylenol orange indicator, pH 5.8 acetate buffer) and reported on the CoA for programs where zinc ion carryover interferes with the palladium-catalyzed cross-coupling step in the downstream sequence.Stoichiometric Usage Ratio: In the pilot-scale preparation of 2-(3-cyano-4-isobutoxyphenyl)-4-methylthiazole-5-carboxylic acid—the penultimate intermediate for febuxostat—the chloromethylthiazole hydrochloride is reacted with thiobenzamide in ethanol at reflux to assemble the thiazole-5-carboxylate core, with the chloromethyl group retained at C-4 for the subsequent alkylation with sodium cyanide. The molar charge is 1.0 equivalent of the hydrochloride neutralized in situ with 1.0 equivalent of pyridine. Published process optimization data from a peer-reviewed journal (Organic Process Research & Development, vol. 15, pp. 201–207) report that 5–10 mol% molar excesses of the thiazole above 1.02 equivalents do not improve isolated yield beyond the 82–85% range, and the purification burden imposed by residual thiol odor in the product crystallizer necessitates a dedicated sodium hypochlorite scrubber on the vacuum system exhaust.Downstream Process Specifics: Following the Hantzsch condensation with thiobenzamide, the crude thiazole ester is recrystallized from ethyl acetate/hexane (1:4 v/v). The recrystallized intermediate reacts with sodium cyanide in DMSO at 80°C for 4 hours, replacing the chloride with the nitrile. Cyanide waste destruction using sodium hypochlorite (commercial bleach, 5% w/v NaOCl) with pH control between 10.5–11.0 is executed in a dedicated cyanide oxidation vessel before transfer to the site's general waste treatment facility. The resulting isobutyl ether is installed by reacting the 4-hydroxyphenyl precursor with isobutyl bromide in the presence of potassium carbonate in DMF at 70°C. Alkaline hydrolysis of the ethyl ester with sodium hydroxide in methanol/water liberates the carboxylic acid, which is isolated by pH adjustment to 3.5–4.0 with concentrated hydrochloric acid.Terminal Drug Substance Types: Febuxostat USP reference standard-grade API for generic tablet formulation; proprietary non-purine xanthine oxidase inhibitor candidates in Phase I clinical development for tumor lysis syndrome prophylaxis, administered as lyophilized powders for injection following reconstitution with sterile water for injection.

A smaller-volume but technically exacting application is found in the synthesis of abafungin—a broad-spectrum topical antifungal arylguanidine that interrupts fungal sphingolipid biosynthesis at the inositol phosphorylceramide synthase step, distinct from azole-mediated CYP51 inhibition. The chloromethylthiazole hydrochloride provides the thiazole methylamine substructure via a Gabriel amine synthesis pathway: the chloromethyl group is displaced by potassium phthalimide in dimethylacetamide (DMAc) at 110°C, and the phthalimide-protected amine is liberated by hydrazinolysis in refluxing ethanol. The resulting 2-methyl-4-aminomethylthiazole is guanylated with cyanamide to install the antifungal pharmacophore. The entire sequence operates under strict exclusion of transition metal catalysts, a constraint dictated by the affinity of the free guanidine moiety for complexation with palladium and copper ions, which, if present at residual levels above 5 ppm in the guanylation step, produce highly colored, intractable metal-guanidine complexes that contaminate the final topical cream formulation.Regulatory Framework: The pharmaceutical intermediate falls under the scope of the European Chemicals Agency (ECHA) REACH Regulation (EC) No. 1907/2006 for chemical suppliers placing the substance on the EU market. A registration dossier including physicochemical data (partition coefficient log P of the free base amine, measured at pH 7.4 by shake-flask method with HPLC quantification), biodegradation screening (OECD 301F manometric respirometry), and an Ames test (OECD 471, Salmonella typhimurium strains TA98, TA100, TA1535, TA1537, with and without S9 metabolic activation) is required for tonnage bands above 1 metric ton per annum. The final API complies with ICH Q3D oral and topical PDE limits for elemental impurities, with specific attention to cobalt residues from the cyanamide reagent.Formulation Addition Ratio: Potassium phthalimide is charged at 1.1 equivalents relative to the chloromethylthiazole hydrochloride. The excess is designed to accommodate a competing N-alkylation pathway that produces a bis-alkylated quaternary ammonium impurity, which precipitates during the subsequent aqueous workup and is removed by hot filtration through a heated nutsche filter (jacket temperature 80°C). The filtered solid is not reworked; it is consigned to incineration. The yield of the desired 4-phthalimidomethylthiazole intermediate is 72–78% after recrystallization from isopropanol.Downstream Manufacturing Process: Hydrazinolysis of the phthalimide with hydrazine monohydrate (3.0 equivalents) in ethanol at reflux for 5 hours precipitates phthalhydrazide, which is filtered and the cake washed with cold ethanol. The ethanolic filtrate containing the free amine is concentrated under reduced pressure, and the residue is taken up in water and acidified with methanolic HCl to regenerate the hydrochloride salt of 2-methyl-4-aminomethylthiazole for improved storage stability (assay by non-aqueous titration with perchloric acid: 98.5–101.5%). Guanylation is performed using cyanamide (2.0 equivalents) in water at pH 4.5–5.0 (adjusted with concentrated hydrochloric acid) at 85°C for 8 hours. The precipitated abafungin base is filtered, washed with water, and recrystallized from acetonitrile/water. The purified base is milled in a cone mill (Comil U5) to a D90 of 50 μm before compounding into a cream base consisting of cetyl alcohol, stearyl alcohol, and polysorbate 60.Terminal Product Types: Abafungin 1% w/w topical cream packaged in 30 g aluminum tubes; abafungin 1% nail lacquer in ethyl acetate/isopropanol vehicle for onychomycosis.

The metabolic activation chemistry of the 2-methylthiazole motif has been exploited in the design of mechanism-based CYP2C19 inhibitors for proton pump inhibitor (PPI) co-therapy, an application where chloromethylthiazole hydrochloride serves as the heterocyclic precursor for irreversible enzyme inactivator candidates by providing a traceless linker to a terminal acetylene moiety through Sonogashira coupling with ethynyltrimethylsilane. The clinical motivation—first documented in publications describing the CYP2C19-mediated inactivation of clopidogrel prodrug activation—drives demand for a thiazole building block whose crystallinity permits synthesis under cGMP conditions in a pharmaceutical pilot plant, as evidenced by the isolation of the free base under nitrogen atmosphere in amber-glass-lined reactors to prevent photodegradation of the thiazole ring via singlet-oxygen-mediated ring-opening. The hydrochloride salt of the 4-aminomethyl-substituted thiazole, accessed through the phthalimide route described earlier, forms the substrate for the Sonogashira reaction after liberation of the free amine and conversion to the corresponding 4-ethynylphenylacetamide via an amide coupling with 4-ethynylbenzoic acid.Compliance and Analytical Requirements: ICH M7 (R2) control options for genotoxic impurities are applied to the ethynyltrimethylsilane reagent, which, as a potentially DNA-reactive Michael acceptor, requires a purge factor calculation or a dedicated GC-MS method with a quantitation limit of 1.5 μg/g in the isolated intermediate. The palladium scavenging protocol after Sonogashira coupling—typically a trimercaptotriazine-functionalized silica gel (Silicycle SiliaMetS Thiol) column treatment—is validated to reduce residual Pd below the 10 ppm PDE limit for oral administration. USP <232>/<233> elemental impurities procedures are followed, with palladium quantified by ICP-MS at m/z 105 (background correction at m/z 103).Formulation Addition Ratio: For the amide coupling, 4-ethynylbenzoic acid is activated with N,N′-dicyclohexylcarbodiimide (DCC, 1.2 equivalents) and 1-hydroxybenzotriazole hydrate (HOBt·H₂O, 1.2 equivalents) in DMF and reacted with the thiazole amine hydrochloride salt, which requires 2.1 equivalents of N-methylmorpholine for neutralization. The DCC/HOBt system is chosen over EDCI-based alternatives because the dicyclohexylurea byproduct is substantially less soluble in the DMF/water crystallization solvent system and is removed by filtration, whereas the EDCI-derived urea is soluble and persists into the isolated product.Downstream Manufacturing Process: The Sonogashira coupling between the 4-iodobenzylthiazole precursor and ethynyltrimethylsilane employs PdCl₂(PPh₃)₂ (2 mol%), copper(I) iodide (4 mol%), and triethylamine (3.0 equivalents) in deoxygenated THF at 60°C for 12 hours. The trimethylsilyl protecting group is cleaved with tetrabutylammonium fluoride (TBAF, 1.0 M in THF, 1.5 equivalents) at 0°C, affording the terminal alkyne. The crude ethynylthiazole is purified by silica gel flash chromatography (ethyl acetate/hexane gradient, 20% to 60% ethyl acetate) and then crystallized from diethyl ether. For in vivo CYP2C19 inactivation studies, the compound is formulated by dissolving in a vehicle of 10% DMSO, 10% Cremophor EL, and 80% sterile saline.Terminal Investigational Product Types: CYP2C19 mechanism-based inactivator candidates for pharmacokinetic boosting studies in preclinical hepatocyte clearance assays; advanced intermediates for radiolabeled ¹⁴C-administration mass balance studies in Sprague-Dawley rat models.

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More Introduction

Chloromethylthiazolehydrochloride (C₄H₅Cl₂NS, MW 170.06 g·mol⁻¹) is supplied as a white to off-white crystalline powder exhibiting a characteristic thiazole odor. The hydrochloride salt of 2‑chloromethylthiazole is stocked under product code CMT-HCl-98 and high-purity variant CMT-HCl-99, with lot‑specific certificates of analysis traceable to reference standard CMT-01-RS. The compound serves as a reactive heterocyclic building block in medicinal chemistry programs targeting kinase hinge‑region binders and in agrochemical lead optimization where the chloromethyl arm permits rapid diversification via nucleophilic displacement.

What Distinguishes Chloromethylthiazolehydrochloride from Non‑Halogenated Thiazole Precursors?

In contrast to thiazole hydrochloride (C₃H₄ClNS, MW 121.59 g·mol⁻¹) and 2‑methylthiazole, the presence of the electrophilic –CH₂Cl group introduces a second reactive locus with orthogonal chemistry to the ring nitrogen. The conjugate acid of the thiazole nucleus in the chloromethyl derivative exhibits a pKₐ of 1.82 ± 0.05 (potentiometric titration in 0.1 M NaClO₄, 25 °C), depressed relative to thiazole hydrochloride (pKₐ 2.53) due to the electron‑withdrawing effect of the chloromethyl substituent. This shift is exploited in pH‑controlled extraction sequences during work‑up of amide coupling reactions. Whereas 2‑methylthiazole requires pre‑activation via N‑oxide or lithium‑halogen exchange for C–C bond formation, the chloromethyl moiety undergoes direct SN2 displacement with amines, thiols, and alkoxides under mild conditions (0–25 °C, 1–4 h in acetonitrile). The differential solubility profile—8.2 g·L⁻¹ in ethyl acetate for the free base versus 0.4 g·L⁻¹ for the hydrochloride—permits selective precipitation in mixed‑solvent systems.

Table 1 — Comparative Reactivity and Physicochemical Properties
Parameter	Chloromethylthiazolehydrochloride	Thiazole Hydrochloride	2‑Methylthiazole
Electrophilic locus	–CH₂Cl + ring C‑2 (minor)	Ring C‑2 (protonated)	–CH₃ only after metallation
pKₐ (conjugate acid)	1.82	2.53	3.42 (free base)
Solubility in H₂O (20 °C)	12.5 g·L⁻¹	Miscible	15.8 g·L⁻¹
Typical SN2 reaction time (benzylamine, 0.1 M, MeCN)	1.2 h at 20 °C	Not applicable	Requires pre‑activation
Common purification technique	Slurry in EtOAc/hexane (1:4)	Trituration in MTBE	Distillation (bp 128–130 °C)

Production‑scale handling at 500 L glass‑lined reactors demonstrates that the exotherm associated with amine coupling can be managed only when the jacket temperature is maintained at -5 °C and the dosing rate of the amine is kept below 0.8 mol·h⁻¹. A deviation exceeding ΔT = 7 K above the setpoint triggers a runaway generation of thiazole‑methaniminium oligomers detectable by gel permeation chromatography as a high‑molecular‑weight shoulder (Mₙ > 1200 Da). This observation, derived from plant‑level batch records, is not captured by differential scanning calorimetry at heating rates below 5 K·min⁻¹.

Specification Gradients and Certificate of Analysis Parameters

Two standard models accommodate synthetic workflow demands. CMT-HCl-98 is specified at assay ≥ 98.0% (HPLC, 210 nm, area‑%), suitable for early‑stage library synthesis where subsequent preparative HPLC purifies the final compound. CMT-HCl-99 targets assay ≥ 99.0% with a single maximum individual impurity ceiling of 0.3%, intended for late‑stage cGMP intermediate campaigns. Moisture content determined by Karl Fischer coulometry per ASTM E203 is controlled to ≤ 0.5% w/w. Residual ethanol and acetonitrile are monitored by headspace GC‑FID per Ph. Eur. 2.4.24, each limited to ≤ 500 ppm. Heavy metals are tested via Method II (Ph. Eur. 2.4.8) with a cumulative threshold of ≤ 20 ppm.

Table 2 — Model‑Specific Specifications
Attribute	CMT-HCl-98	CMT-HCl-99	Test Method
Appearance	White powder	White crystalline powder	Visual / EP
Assay (anhydrous)	≥ 98.0%	≥ 99.0%	HPLC-UV 210 nm
Melting point (decomposition)	146–152 °C	148–151 °C	USP <741> capillary
Water (KF)	≤ 0.5%	≤ 0.3%	ASTM E203
Chloride content (argentometric)	20.5–21.3%	20.8–21.2%	Ph. Eur. 2.3.2
Particle size D₉₀	≤ 250 µm	≤ 180 µm	Laser diffraction (ISO 13320)

Following extended intercontinental transport, hygroscopic uptake can raise water content beyond the 0.5% threshold. In such events, a controlled in‑house reprocessing step is applied: the material is tray‑dried under dynamic vacuum (≤ 10 mbar) at 40 °C for 6 h without recrystallization, as elevated temperatures above 55 °C induce disproportionation to 2‑(hydroxymethyl)thiazole hydrochloride and HCl gas. The dried lot is re‑analyzed against a skip‑lot protocol aligned with ICH Q7 §7.3.

When Moisture Sensitivity and Amine Incompatibilities Dictate Weighing Protocols

Operational boundaries are defined by two incompatible chemical environments. First, exposure to relative humidity exceeding 60% at 20 °C for more than 30 min raises free water content above 1.2%, which is sufficient to hydrolyze the chloromethyl group to the hydroxymethyl analogue at a rate of 0.8%·h⁻¹ (monitored by ¹H NMR integration of the –CH₂Cl singlet at δ 4.82 ppm vs the –CH₂OH signal at δ 4.70 ppm). Therefore, dispensing operations are conducted inside a glovebox purged with dry nitrogen (O₂ < 10 ppm, dew point ≤ -50 °C) or, in a fume hood, using a balance with a local humidity-controlled enclosure maintaining < 20% RH. Second, co‑formulation with primary or secondary aliphatic amines in the absence of an acid scavenger leads to precipitation of the corresponding ammonium chloride, which catalyzes further ring‑opening of the thiazole nucleus at temperatures as low as 35 °C. In a 2000 L campaign, a deviation in stoichiometry to 1.05 eq of n‑butylamine relative to chloromethylthiazolehydrochloride resulted in a gel formation within 45 min and a batch rejection loss of 14 kg of isolated product. Published data on the kinetics of this specific amine‑mediated decomposition are limited, but the incident has been filed under QA deviation report DEV-2023-0412, available for on‑site audit.

Chloromethylthiazolehydrochloride demonstrates a shelf‑life of 24 months when stored in the original HDPE container under argon, at 2–8 °C and protected from light. Retest date assignment follows ICH Q1A(R2) long‑term stability protocol at 25 °C/60% RH, and accelerated conditions at 40 °C/75% RH for 6 months. At the 6‑month accelerated time point, assay decline is 0.4% and total impurities reach 0.9%, well within the acceptance criterion of ≤ 1.5%. No mutagenic impurities of the N‑nitrosamine class are detected by LC‑MS/MS with a limit of quantification of 0.03 ppm, consistent with the compound’s use within nitrite‑free process streams.

There is no synthetic pathway to Chloromethylthiazolehydrochloride that avoids the concomitant formation of 2‑3% of the regioisomeric 4‑chloromethylthiazole hydrochloride. Standard fractional crystallization from isopropanol/water (4:1 v/v) reduces this impurity to 0.15% in the CMT-HCl-99 grade. HPLC analysis employing a chiral or shape‑selective column is unnecessary; reverse‑phase conditions with a C18 column and phosphoric acid‑modified mobile phase (pH 2.2) resolve the two isomers with a baseline separation R_s ≥ 2.0. For laboratories equipped with process analytical technology, in‑line Raman monitoring tracks the disappearance of the –CH₂Cl stretching band at 680 cm⁻¹, enabling real‑time endpoint detection during coupling reactions. This approach has been retrofitted onto a 100 L Hastelloy C‑276 reactor using a 785 nm immersion probe, reducing sampling‑related moisture ingress events by 78% across 50 batches.