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

Under an argon-blanketed atmosphere in a jacketed 2000 L glass-lined reactor fitted with a retreat-curve impeller and a baffle, 2-bromo-4-phenylthiazole (1.0 eq, 238.1 g/mol) is charged into a previously degassed mixture of toluene and deionized water (4:1 v/v, degassed by three vacuum/nitrogen purge cycles until residual oxygen measured by an Orbisphere 410 sensor remains below 50 ppb). The coupling component, 4-cyano-3-fluorophenylboronic acid pinacol ester (1.18 eq), is then added together with tetrakis(triphenylphosphine)palladium(0) (0.25 mol% relative to bromide) and anhydrous tribasic potassium phosphate (2.2 eq, milled to a particle size D50 ≤ 45 μm for improved phase-transfer kinetics). The batch is brought to 78 ± 2 °C under a jacket setpoint cascade tuned to a ΔT log-mean of 12 °C, and the conversion is monitored by in-line ReactIR 15 equipped with a diamond ATR probe, tracking the disappearance of the C–Br stretch at 1058 cm⁻¹; full consumption is typically observed at 14–16 hours. Post-reaction, the ternary mixture is cooled to 35 °C, diluted with ethyl acetate, and passed through a 0.5 m² plate filter precoated with Celite 545 to remove palladium black. The organic phase is washed with 5% w/w aqueous N-acetyl-L-cysteine (pH 7.2) for selective Pd scavenging, reducing residual Pd to ≤ 5 ppm as measured by ICP-MS on an Agilent 7900 instrument against a certified palladium standard (NIST SRM 3114). Compliance with ICH Q7 Section 8 (Production and In-Process Controls) and USP <467> Class 2 residual solvent limits is mandatory for batches destined for GLP toxicology lots; the isolated biaryl intermediate is dried in a double-cone vacuum dryer at 45 °C, 25 mbar, to a toluene content ≤ 890 ppm. This biphenylthiazole scaffold subsequently enters a hydrozone formation and cyclodehydration sequence catalyzed by p-toluenesulfonic acid (0.05 eq) in refluxing toluene to yield triazolothiazole candidates that function as lanosterol 14α-demethylase (CYP51) inhibitors—a terminal product class comprising second-generation azole antifungals evaluated against fluconazole-resistant Candida auris isolates (MIC₉₀ values determined by CLSI M27-A4).

The data illustrate the trade-off between cycle time and palladium scavenging efficiency; the Pd(PPh₃)₄ entry provides the lowest residual Pd burden but requires extended reaction time, a factor that impacts throughput in a 2000 L train operating at a 7-day campaign cycle.

What Governs the Regioselectivity of Buchwald‑Hartwig Amination at the C2 Bromo Position in the Presence of the 4‑Phenyl Substituent?

In the context of thiazolecarboxamide fungicides targeting succinate dehydrogenase (SDHI class), the 2-bromo substituent operates as a traceless reactive handle for the introduction of substituted aniline nucleophiles. The electron-withdrawing character of the thiazole ring activates the C2 position for oxidative addition, yet the steric influence of the adjacent 4-phenyl group can direct the active Pd^II–amide intermediate toward β-hydride elimination pathways if the base strength and ligand bite angle are not strictly tuned. A production-scale protocol employs a pre-catalyst mixture of Pd₂(dba)₃ (0.5 mol%) and Xantphos (1.1 mol%) in anhydrous 1,4‑dioxane (KF ≤ 100 ppm) with degassed 2.0 M aqueous K₃PO₄ as the base reservoir. The aryl bromide component is charged at 1.0 eq, while the amine coupling partner—typically 2-amino-3-chloro-5-trifluoromethylpyridine or its bromo analog—is loaded at 1.08 eq to suppress diarylamine impurity formation. The reaction mixture is sparged with argon through a sintered metal frit for 25 min before heat-up, and the jacket temperature is ramped to 105 °C over 40 min; the pot temperature is then held at 99 ± 2 °C for 6–8 h under a slight positive pressure of 0.2 bar. Sampling every 60 min for UHPLC analysis (column: Acquity UPLC BEH C18 1.7 µm, gradient: 5→95% MeCN in 0.1% formic acid) quantifies the residual bromide; the endpoint is defined at ≤ 0.5% area% remaining. Upon completion, the batch is cooled to 25 °C, diluted with ethyl acetate, and washed with 3% w/w aqueous citric acid to remove palladium species, followed by brine and a 1% w/w EDTA‑4Na solution. The organic layer is filtered through a 0.2 µm polypropylene filter cartridge and concentrated under reduced pressure (40 °C, 80 mbar) to a target potency of 95.0% w/w (HPLC). Residual Pd in the intermediate must be ≤ 12 ppm to meet the downstream hydrogenation catalyst tolerance; values are verified using an Agilent 5800 ICP-OES calibrated with a multi-element standard traceable to NIST SRM 3162. The isolated N-arylated product is a direct precursor to thiazolecarboxamides that exhibit in-vitro activity against Rhizoctonia solani and Botrytis cinerea at ED₅₀ below 0.5 µg/mL. Regulatory compliance follows the FAO/WHO Joint Meeting on Pesticide Specifications (JMPS) manual, with particular attention to FAO Specification 406/TC for technical grade active ingredient, EP 5.1.3 for relative substances, and the US EPA 40 CFR § 180.671 for field trial residue tolerance. A representative terminal product is a 20% w/v suspension concentrate (SC) formulation loaded with the carboxamide active, delivered into rice blast management programs through ground application at 120 g a.i./ha.

Solution-processable electron transport layers (ETLs) in inverted organic photovoltaic devices increasingly incorporate thiazole-flanked naphthalene diimide copolymers to achieve LUMO levels near −3.9 eV while maintaining solubility in non‑chlorinated solvents such as anisole or 2‑methyltetrahydrofuran. Synthesis of these donor‑acceptor copolymers starts from 2‑bromo‑4‑phenylthiazole, which serves as the brominated acceptor monomer for a Migita–Kosugi–Stille cross-coupling with a stannylated bithiophene donor unit (5,5′-bis(trimethylstannyl)-2,2′-bithiophene) under inert conditions. A 50 L jacketed glass reactor equipped with a turbine agitator and a reflux condenser connected to a silicone oil temperature control unit is charged with the two monomers at a strictly maintained molar ratio of 1.000:1.002 (donor:acceptor) to target a number-average molecular weight (Mₙ) of 25–35 kDa, as deviation beyond ±0.5% leads to uncontrolled polydispersity values exceeding 3.2 and poor film-forming morphology. The catalyst system uses Pd₂(dba)₃ (2 mol%) and tri(o‑tolyl)phosphine (8 mol%) in degassed chlorobenzene (KF < 30 ppm), polymerized at 130 °C for 48 h under a gentle argon flow. The crude polymer is end-capped by sequential addition of 2‑bromothiophene and tributyl(thiophen‑2‑yl)stannane (0.05 eq each) to remove reactive chain termini. Following precipitation into methanol containing 2% v/v ethylenediamine, the polymer undergoes Soxhlet extraction with methanol, acetone, and hexane to strip low‑molecular‑weight oligomers, then is dissolved in chloroform and passed through a mixed‑bed column of activated carbon and silica gel. For electronic‑grade specification, the material is subsequently purified in a Zhejiang SM Technology TSD‑850 multi‑zone gradient sublimation furnace at a base pressure ≤ 6 × 10⁻⁷ Torr; the deposition zone is held at 385 °C while the cold finger is maintained at 22 °C, a temperature window that must not fluctuate more than ±1.5 °C to prevent visible agglomeration on the cold surface. Each sublimate batch is assayed by glow discharge mass spectrometry (GD‑MS) for elemental impurities and must meet the SEMI C8‑0318 Grade 2 requirements for electronic chemicals, with Na, K, and Fe each ≤ 50 ppb. The final powder is then formulated as a 5 mg/mL solution in anisole:indane (4:1 v/v) and slot‑die coated onto ITO/ZnO substrates in a cleanroom (ISO Class 5) to yield an electron transport layer with average electron mobility of 4.2 × 10⁻⁴ cm²/V·s measured via the space‑charge limited current (SCLC) method (device structure: ITO/Al/MoO₃). Compliance with IEC 62321‑3‑1:2013 for RoHS restricted substances and with IEC 61249‑2‑21 for halogen content in printed boards ensures that the material can be integrated into consumer‑grade flexible OLED panels; terminal products include large‑area (100 cm²) printed lighting panels and wearable electrocardiogram sensor displays.

Luminescent Ratiometric Probes Targeting Mitochondrial Cu(I) Pools

A thiazole‑derived chelating motif built from 2‑bromo‑4‑phenylthiazole forms the core of a ratiometric fluorescent probe designed to detect labile copper‑I pools in the mitochondrial intermembrane space with a dissociation constant K_d near 3.2 × 10⁻¹² M. The synthetic sequence begins by displacing the C2 bromide with sodium azide (1.5 eq) in dry DMF at 55 °C for 4 h, followed by CuAAC click conjugation to an alkyne‑functionalized Rhodamine B amide derivative (1.0 eq) using a CuSO₄·5H₂O/sodium ascorbate catalytic system (0.1 eq/0.2 eq) in 1:1 water/tert‑butanol at ambient temperature under argon for 12 h. The crude conjugate is purified on a preparative HPLC system (YMC‑Pack ODS‑A 20 mm × 250 mm, 10 µm) eluting with a gradient of acetonitrile and ammonium formate buffer (20 mM, pH 6.8), yielding the trifluoroacetate salt with ≥ 98.5% area purity (HPLC‑DAD, 254 nm). For live‑cell imaging applications, the probe is reconstituted in HEPES‑buffered saline (20 mM, pH 7.4) containing 0.1% Pluronic F‑127 and loaded into HeLa cells at a final working concentration of 2.5 µM; the formulation is compliant with ISO 13485:2016 quality management for in‑vitro diagnostic device components, and the stock solution is tested for endotoxins according to USP <85> (limit < 0.5 EU/mg) prior to release. The production process for the probe precursor, 2‑azido‑4‑phenylthiazole, is conducted at 500 g scale in a 10 L jacketed reaction vessel under nitrogen, and the azide intermediate, classified as a potentially explosive substance, is never isolated as a dry solid; it is kept in DMF solution (15% w/w) and stored at ≤ 8 °C for a maximum of 72 h before the subsequent click step. The terminal product class encompasses a family of thiazole‑tagged rhodamine reporters distributed as lyophilized aliquots in 50 µg vials, intended for confocal laser scanning microscopy excitation at 561 nm with ratiometric emission monitored at 580 nm and 625 nm; these reagents are utilized in metalloneurochemistry studies to quantify mitochondrial copper trafficking defects in iPSC‑derived dopaminergic neurons as disease models for early‑onset Parkinson’s.

When 2‑Bromo‑4‑phenylthiazole Serves as a Precursor to P,N‑Bidentate Ligands for Asymmetric Allylic Alkylation

The phosphination of the thiazole scaffold to generate a hemilabile P,N‑bidentate ligand is executed via a lithium‑halogen exchange at ‒78 °C. In a 2 L four‑necked round‑bottom flask equipped with a cryogenic thermometer and an addition funnel, 2‑bromo‑4‑phenylthiazole (1.0 eq, 50.0 g) is dissolved in anhydrous THF (0.4 M) and cooled by a dry ice‑acetone bath under argon. n‑Butyllithium (2.5 M in hexanes, 1.02 eq) is added dropwise at a rate that does not allow the internal temperature to exceed ‒72 °C; the resulting orange solution is stirred for 45 min at ‒78 °C before chlorodiphenylphosphine (1.05 eq) is introduced. The mixture is allowed to gradually warm to 0 °C over 3 h, then quenched with degassed ammonium chloride solution. After extraction with ethyl acetate and column chromatography on neutral alumina (eluent: hexane/ethyl acetate 9:1), the phosphine product, obtained as an off‑white solid in 78–83% yield with a phosphorus content ≥99.0% by ³¹P NMR (singlet at δ −4.10 ppm referenced to 85% H₃PO₄ external standard), is stored under argon at ‒20 °C to prevent oxidation. For catalytic application, this ligand is paired with [Pd(η³-allyl)Cl]₂ at a ligand‑to‑metal molar ratio of 2.2:1 (0.5 mol% Pd) in anhydrous dichloromethane; the allylation of dimethyl malonate with (E)-1,3‑diphenyl‑2‑propen‑1‑yl acetate proceeds to ≥ 95% conversion in 4 h at 25 °C with an enantiomeric excess of 92–94% (chiral HPLC on a Chiralcel OD‑H column, hexane/i‑PrOH 95:5, 1.0 mL/min). Asymmetric amplification experiments reveal a marked positive non‑linear effect, requiring rigorous exclusion of water ( ≤ 20 ppm in solvent) to avoid ligand protonolysis. Production for kilogram‑scale research supply follows ISO 9001:2015 quality protocols, with pre‑release analysis including Karl Fischer titration, ³¹P{¹H} NMR purity, and chiral HPLC verification. The terminal products are optically active 1,3‑dicarbonyl derivatives and allylic amines that serve as building blocks for phase‑III chemokine receptor antagonists, thus linking the thiazole phosphine technology to late‑stage pharmaceutical intermediates produced under cGMP guidelines incorporated by reference from ICH Q11 starting material designation.

A scalable SNAr route installs 2‑alkoxy or 2‑thioalkyl groups on the 4‑phenylthiazole nucleus by taking advantage of the activating effect of the electron‑deficient C2 position. In a development campaign for peroxisome proliferator‑activated receptor delta (PPAR‑δ) agonists based on a 4‑phenylthiazole hinge‑binder pharmacophore, 2‑bromo‑4‑phenylthiazole is reacted with ethyl 2‑mercaptoacetate (1.3 eq) in the presence of milled anhydrous potassium carbonate (1.5 eq) in acetonitrile (8 volumes) inside a 100 L glass‑lined reactor. The suspension is heated to gentle reflux (82 °C) with vigorous overhead stirring at 180 rpm for 9 h, after which IPC by GC‑FID (column: Restek Rxi‑5Sil MS 30 m × 0.25 mm, temperature program 80→280 °C) shows bromide conversion of  ≥ 99.3%. The cooled mixture is filtered through a Nutsche filter to eliminate inorganic salts, and the filtrate is concentrated under vacuum (45 °C, 35 mbar) to a dark oil that is crystallized from ethanol/water (3:1 v/v, 0 °C) to afford colorless plates of the thioether intermediate with DSC peak purity  ≥ 99.9% (onset melting point 84.8 °C, enthalpy 114 J/g). The isolated intermediate carries a residual bromide limit of  ≤ 0.15% w/w (ion chromatography on a Dionex ICS‑6000) and is subsequently hydrolyzed, coupled with a sulfonamide fragment, and elaborated to the final PPAR‑δ modulator under a quality agreement that references ICH Q7 Section 12 for validation of critical process parameters. The regulatory framework for toxicology batches includes compliance with OECD GLP Principles (ENV/MC/CHEM(98)17) and impurity characterization per EMA ICH M7(R1) for potentially mutagenic impurities; the 2‑bromo‑4‑phenylthiazole starter is itself purified by fractional distillation under nitrogen (bp 142–143 °C / 4 mbar) before use, reducing any charge‑related single impurity to  ≤ 0.10%. The terminal dosage form is a tablet containing the PPAR‑δ receptor modulator in a micronized state (D₉₀ ≤ 8 µm) blended with lactose monohydrate and croscarmellose sodium, administered in clinical trials at daily doses of 2.5 mg and 10 mg for evaluating dyslipidemia endpoints.