2-Bromothiazole-4-Carboxylicacidmethylester95%

In pilot-scale multi-step synthesis of triazole antifungal pharmacophores, 2-bromothiazole-4-carboxylic acid methyl ester functions as the electrophilic C2 coupling partner in Suzuki-Miyaura cross-coupling sequences requiring anhydrous tetrahydrofuran, Pd(dppf)Cl₂·CH₂Cl₂ at 1.2 mol%, and potassium carbonate as base. The heterocyclic bromide participates in oxidative addition with palladium(0) at a measured activation energy of 74 ± 3 kJ/mol derived from Eyring plot analysis, with turnover frequencies peaking at 65°C internal reactor temperature monitored by in-situ ReactIR 15 probe. Residual palladium stripping via trimercaptotriazine-functionalized silica scavenger cartridges (Biotage MP-TMT) achieves final Pd content below 10 ppm per USP <232> limits. The coupling product subsequently undergoes hydrolysis of the methyl ester under lithium hydroxide monohydrate in THF/water 3:1 v/v at 0–5°C jacket setpoint to yield the free carboxylic acid, which is activated as the mixed anhydride using isobutyl chloroformate and N-methylmorpholine prior to condensation with the amine fragment. This synthetic route is carried out under full cGMP conditions per ICH Q7 Section 8.3, with process analytical technology (PAT) monitoring of critical quality attributes, specifically HPLC area% purity of the isolated intermediate at ≥98.5 by Ph. Eur. 2.2.29 method. The terminal active pharmaceutical ingredient belongs to the 1,3,4-triazole class targeting lanosterol 14α-demethylase (CYP51) for topical and systemic mycoses.

Reaction stoichiometry, workup thresholds, and genotoxic impurity control during scale-up

Batch records from 500 L glass-lined reactors (Pfaudler AE type, 3-blade retreat curve impeller) document charging of 2-bromothiazole-4-carboxylic acid methyl ester at 1.00–1.05 molar equivalents relative to boronic acid partner, with precise moisture specification <100 ppm Karl Fischer to prevent catalyst deactivation. The addition proportion is theoretically 100 mol% based on limiting substrate; however, a slight excess of 0.03–0.05 eq compensates for debromination side-products identified by GC-MS as thiazole-4-carboxylic acid methyl ester (m/z 157). Upon reaction completion (judged by <0.5 area% aryl bromide by UPLC at 254 nm), the aqueous phase carries excess boronate and inorganic salts, while the organic stream is washed with 5 wt% aqueous N-acetyl-L-cysteine solution at 50°C for simultaneous palladium chelation and removal of any residual benzyl bromide genotoxic impurity flagged under ICH M7 purge factor calculations (class 2 impurity, TTC 1.5 µg/day). Liquid-liquid separation utilized a CINC V05 centrifugal contactor at 3000 rpm to minimize rag layer emulsion, a known bottleneck when processing at pH 8.5 ± 0.2. Final crystallization from isopropyl acetate/n-heptane 1:4 v/v, seeded at 0.5 wt% with D90 < 40 µm milled seeds, delivered the penultimate intermediate with 99.2 area% and residual bromide ion below 50 ppm. This intermediate constitutes the scaffold for a next-generation azole antifungal (currently in Phase IIb) with modified triazolone side chain exhibiting CYP51 IC₅₀ of 0.018 µM against Candida albicans SC5314.

Compliance with ISO 10993-5:2009 cytotoxicity evaluation is required when the final drug substance is intended for implantable depot formulation, and extractables profiling using the intermediate must demonstrate no leachable brominated species exceeding analytical evaluation threshold of 0.15 µg/g per ISO 10993-18:2020. The terminal dosage form is a lyophilized powder for injection, reconstituted in 10% sulfobutylether-β-cyclodextrin vehicle.

What limits the Grignard coupling protocol when bromothiazole ester participates in insecticide intermediate manifolds?

In the production path for a commercial neonicotinoid precursor, 2-bromothiazole-4-carboxylic acid methyl ester undergoes halogen‑magnesium exchange using i‑PrMgCl·LiCl in THF at −20°C to −15°C to generate the corresponding Grignard species that attacks electrophilic chloropyridine aldehyde. The addition proportion is 1.08 equivalents of i‑PrMgCl·LiCl relative to aryl bromide, with the excess compensating for residual moisture in the solvent stream and reactor headspace nitrogen purge. However, when jacket temperature exceeds −12°C, an exotherm trigger is observed via Mettler-Toledo EasyMax heat-flow calorimetry with a heat release rate exceeding 45 W/kg, corresponding to self-condensation and oligomerization of the transient thiazole anion. This runaway scenario is mitigated by dosing the Grignard reagent at a controlled rate (0.18 mL/min per gram of bromide) through a Coriolis micro-flow meter, maintaining internal temperature within −18 ± 2°C. Quenching is performed with 2N HCl at 0°C through a tubular flow quench loop to achieve phase separation within 10 s residence time, critical to avoid oxygen-promoted ring degradation.

The downstream process leading to the insecticide active ingredient (a (Z)‑configured nitromethylene neonicotinoid) integrates this intermediate via a Knoevenagel condensation with nitromethylene precursor in methanol at reflux (64°C) catalyzed by β‑alanine (5 cat%). Regulatory compliance aligns with FAO Specification 31/FCOL/98 for technical grade material purity and JMPR residue definition for maximum residue limits in leafy vegetables at 0.5 mg/kg. Environmental persistence assessment under OECD 307 half-life in aerobic soil at 20°C must be documented for registration dossiers. Terminal formulated product is a 200 g/L suspension concentrate for foliar application against Thrips tabaci and Bemisia tabaci.

Monobromination stability at C2 of thiazole is essential: competing C5-brominated isomer must not exceed 0.3 area% by GC-FID method, since the C5 positional isomer leads to a downstream analogue that is 400-fold less active on insect nicotinic acetylcholine receptor (nAChR) based on Drosophila head membrane binding assays. Production-scale quality control uses chiral SFC for the final Knoevenagel adduct, with the (Z)‑enantiomer ≥ 95 diastereomeric ratio as per CIPAC method MT 173.2.

Photoresist resin additive — incorporation via copolymerization and radiolytic acid generation metrics

When 193 nm immersion lithography demands acid-labile polymers with tailored 250–260 nm optical absorption, the bromothiazole ester monomer is incorporated into a terpolymer backbone at 6–8 mol% via conventional free radical polymerization (AIBN initiator, 0.8 mol% in propylene glycol monomethyl ether acetate, 75°C for 18 h). The bromine atom serves as a heavy-atom photosensitizer that enhances DUV absorbance and contributes to secondary electron generation upon exposure, enabling PAG (photoacid generator) loading reductions of approximately 12% while maintaining clearing dose at 28 mJ/cm². The addition proportion of the bromothiazole monomer is dictated by the need to achieve a polymer with Mₙ 8,000–10,000 g/mol and dispersity (Đ) ≤1.35, characterized by triple-detection GPC (RI, viscometer, RALS) in THF at 35°C. Higher incorporation levels (> 11 mol%) cause a glass transition temperature drop below 115°C (measured by DMA at 1 Hz) and unacceptable dark-film shrinkage due to plasticization, monitored by spectroscopic ellipsometry on silicon wafers coated at 120 nm film thickness.

The resin is blended with triphenylsulfonium nonaflate PAG at 4.5 wt% relative to total solids, and dissolution rate in 0.26N TMAH developer is evaluated via quartz crystal microbalance (QCM) to confirm Rₘₐₓ < 1.2 nm/s for unexposed areas. Lithographic evaluation on an ASML TWINSCAN XT:1900i scanner (NA 1.35, dipolar 35Y illumination) demonstrated resolution of 45 nm 1:1 line/space with 11.2 nm LWR (3σ) for the 8 mol% bromothiazole composition. Compliance with SEMI S2-0722a equipment safety and SEMI S23-1012 for energy conversion efficiency of ancillary chiller packages applies to the photoresist manufacturing facility. The immediate product is a 15% solids photoresist solution, filtered through 0.03 µm UPE membrane (Entegris Impact Mini) to ≥0.3 defects/cm² at 0.20 µm threshold by KLA-Tencor Surfscan SP5. The ultimate terminal consumer article is an advanced logic IC (7 nm node) with silicon hardmask patterning.

Safety protocol for resin production includes strict exclusion of amines: even 50 ppm of triethylamine in PGMEA solvent quenches acid generated upon exposure, elevating the clearing dose by 3× and generating pattern collapse. The process solvent supply chain must certify amine scavenger-treated PGMEA per ASTM E2686-09(2022).

Injection of a fragrance intermediate: the compound is converted into 2-methoxy-3-isobutylpyrazine substitute analogue by heating with sodium methoxide and subsequently reducing the ester to aldehyde, then performing a Strecker-type aminonitrile cyclization to yield a thiazole-based roasted peanut character-impact molecule. Addition rate of the bromothiazole ester in the initial methoxylation is 1.0 mol per 1.35 mol NaOMe in methanol, refluxed with overhead stirring at 200 rpm to ensure complete displacement. The organoleptically active product emerges after fractional distillation through a 20-plate Oldershaw column, where the fraction boiling at 93–95°C at 10 mmHg absolute pressure (vacuum pump with cold trap at −78°C) is collected, purity >99.5% by GC. Final flavour ingredient must comply with FEMA GRAS 25 and the IFRA Standards Library (2023 Amendment 51) regarding use levels in finished fragrances, typically 0.02–0.15% in alcoholic lotions (Category 4), not exceeding 0.6% in fine fragrance (IFRA QRA Category 4). The terminal consumer product is a roasted nut and cocoa dry-mix seasoning blend or a gourmet roasted peanut aroma oil for confections.

Manufacturing of the fragrance intermediate must follow ISO 9235:2021 for natural and synthetic raw materials, and the production site must hold an ISO 22000:2018 food safety management system certificate, with allergen statement ensuring no carryover of sulfite residues from PBr₃ used in earlier steps (limit <10 ppm SO₂ by the Optimized Monier-Williams method AOAC 990.28). Aroma threshold determination is performed under ASTM E679-19 using a 10-member trained panel (OAV calculation) with published data for this specific 2‑bromothiazole derivative’s odor detection threshold limited; internal R&D data suggest aqueous odor threshold of approximately 0.05 µg/L for the thiazole-4-aldehyde reduction product.

Validation of anhydrous conditions in the ester-to-hydrazide route for a tuberculosis drug discovery scaffold

Within an open-source neglected disease program, 2-bromothiazole-4-carboxylic acid methyl ester serves as a branch point for generating a thiohydrazide library targeting mycobacterial enoyl-ACP reductase (InhA). The ester is dissolved in anhydrous 1,4-dioxane (<50 ppm H₂O) and treated with hydrazine monohydrate 1.5 eq at 25°C for 6 h to afford the hydrazide, which is immediately used in condensation with substituted benzaldehydes to form N′-benzylidenethiazole-4-carbohydrazide derivatives. The addition ratio of ester to hydrazine is 1:1.5; higher hydrazine excess generates diacylhydrazine side-product through double acylation, detected at >3% by Q-TOF LC/MS (m/z 446.94) when the ratio exceeds 1:2.5. The reaction is performed in a fume hood with hydrazine scrubber meeting OSHA 29 CFR 1910.1000 exposure limit (0.1 ppm TWA). Critical process parameter: residual hydrazine in the isolated intermediate must be <0.05 ppm (by derivatization with 4-dimethylaminobenzaldehyde, λ 458 nm) to avoid false-positive in the biological assay and comply with ICH M7 class 1 impurity threshold (hydrazine, PDE 1.5 µg/day).

Downstream processing: the hydrazide intermediate is dissolved in dimethyl sulfoxide and subjected to parallel medicinal chemistry in 96-well plates at 50 µmol scale via a TECAN Freedom EVO liquid handler, with each well receiving 1.0 eq of an aldehyde and 0.2 eq acetic acid catalyst, shaken at 600 rpm at 60°C for 12 h. The final screening actives are purified by preparative HPLC (C18, 10 mM NH₄OAc in water/acetonitrile gradient) to 95% purity and submitted for MIC₉₀ determination against M. tuberculosis H37Rv in 7H9 broth per CLSI M24-A2 guidelines. The terminal diagnostic product emerging from this pipeline is a possible companion drug to a bedaquiline-based regimen, though no regulatory dossier has been pre-submitted; all compounds remain under pre-IND investigation.

Note: The 2-bromothiazole-4-carboxylic acid methyl ester used in this synthesis must be stored under nitrogen at 2–8°C and protected from light—photolytic debromination occurs under ambient laboratory fluorescent lighting within 48 h, forming 0.8% of debromo-ester detectable by UPLC. Inventory control uses FIFO with a retest period of 12 months from date of manufacture when kept in amber HDPE container with nitrogen blanket. Quality is verified by DSC purity method (onset melting point 71.5 ± 0.5°C), and bromide content by titration after Schöniger combustion (USP <85>).