2-(4-Bromophenyl)-1,3-Thiazole-4-Carbaldehyde

Fragment-based drug discovery (FBDD) against serine/threonine kinase targets routinely exploits the 4-bromophenyl-thiazole aldehyde scaffold as a privileged hinge-binding fragment. When integrated into a library of reversibly covalent inhibitors, the compound is introduced as the electrophilic coupling partner at 1.05 equivalents in a Pd(dppf)Cl₂-catalysed Suzuki–Miyaura reaction with heteroaryl boronic acids bearing a solubilising morpholine or N-methylpiperazine tail. All synthetic operations serving the preparation of active pharmaceutical ingredient (API) intermediates for Phase I clinical candidates are conducted under the quality system defined by ICH Q7 Section 7.3, with residual palladium monitored per ICH Q3D and maintained below 10 ppm. The post-reaction work-up includes an aqueous EDTA disodium salt wash to scavenge residual metal, filtration through a 0.5-µm in-line capsule, and purification by supercritical fluid chromatography (SFC) on a 2-ethylpyridine-bonded phase using a CO₂/methanol gradient, delivering the biaryl intermediate in isolated yields exceeding 82% and with an enantiomeric excess of >99.0% after chiral resolution. The downstream process transfers this key intermediate into a scalable reductive amination with a protected piperidine-4-carbaldehyde, followed by Boc deprotection under aqueous HCl in isopropyl acetate and final crystallisation from methyl tert-butyl ether/n-heptane. The terminal manufactured form is a crystalline free base classified as an orally bioavailable c-Met/ALK dual inhibitor for oncological indications, packed in double anti-static polyethylene bags under argon for shipment to contract dose formulation sites.

When β-Ketoester Condensation Outcompetes Aldol Side-Reaction Pathways

The synthesis of succinate dehydrogenase inhibitor (SDHI) fungicide analogues bearing a thiazole-4-carboxamide pharmacophore demands strict control of the condensation regiochemistry when 2-(4-bromophenyl)-1,3-thiazole-4-carbaldehyde is condensed with ethyl 4,4,4-trifluoroacetoacetate in the presence of ammonium acetate. Process-scale observations on a 100-L jacketed glass-lined reactor with pitched-blade impeller indicate that holding the reaction temperature at 8 ± 2 °C during the addition of the β-ketoester suppresses the competitive aldol self-condensation that generates a chromophoric dimer impurity absorbing at 390 nm. The aldehyde is charged at a stoichiometric ratio of 1.00 equivalent relative to the ketoester, and the acetic acid/sodium acetate buffer maintains the pH between 4.8 and 5.2 for optimal selectivity. Regulatory alignment follows the FAO Manual on Development and Use of FAO Specifications for Plant Protection Products, with particular reference to the November 2022 revision of the 56/TK protocol for technical-grade active substances; ecotoxicological profiling is performed according to OECD Test No. 208 (Terrestrial Plant Test) and OECD Test No. 209 (Activated Sludge Respiration Inhibition). After quench with 10% w/w aqueous ammonium chloride, the organic phase is concentrated under reduced pressure (50–60 mbar, bath temperature 40 °C) and the crude oil is purified by wiped-film short-path distillation at 0.8 mbar with an evaporator jacket temperature of 165 °C, yielding the intermediate dihydrothiazole ester. Subsequent alkaline hydrolysis and HATU-mediated coupling with 2-(trifluoromethoxy)aniline furnishes the free amide, which is formulated as a 200 g/L suspension concentrate (SC) using a styrene-acrylic graft copolymer dispersant and a non-ionic alkoxylated alcohol wetting agent, suitable for foliar application in cereal rust control.

Direct vacuum sublimation of the iridium(III) bis[2-(4-bromophenyl)thiazole-4-carbaldimine]picolinate complex produces a highly purified green electrophosphorescent dopant that is co-evaporated with 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) host in a vacuum chamber at a base pressure of 5 × 10⁻⁷ mbar. The dopant is blended into the emissive layer at a mass fraction of 8–10 wt% relative to the host, a concentration range determined by continuous-wave photoluminescence quantum yield measurements on encapsulated thin films in an integrating sphere configuration per IEC 62321-5 (Determination of cadmium, lead and chromium in polymers and electronics) and elemental purity verification under ASTM E2823-17 (Standard Test Method for Analysis of Nuclear-Grade Plutonium by Glow Discharge Mass Spectrometry, adapted for trace metals in organic matrices). Comprehensive limits for halogen residues are set according to IEC 61249-2-21: total bromine content cannot exceed 900 ppm and total chlorine must remain below 900 ppm, while each individual halide is controlled to < 200 ppm to avoid charge-trapping defects. Purification is executed on a four-zone horizontal gradient sublimation apparatus (Lindberg/Blue M tube furnace) with zone temperatures set at 295 °C (source), 285 °C (baffle), 190 °C (deposition), and 25 °C (cold trap), using high-purity argon carrier gas at a flow rate of 15 sccm. The sublimed material reaches a differential scanning calorimetry melting endotherm with an onset of 342.1 °C and a half-width of 2.3 °C, indicative of 99.95% mass purity by absolute method. The final device structure is an indium tin oxide (ITO) / HAT-CN (10 nm) / NPB (40 nm) / CBP:dopant (30 nm) / Bphen (30 nm) / LiF (1 nm) / Al (100 nm) bottom-emitting phosphorescent organic light-emitting diode, achieving an external quantum efficiency of 18.2% at a luminance of 1000 cd/m². The completed panel is the core component of commercial display modules manufactured under ISO 9001:2015 and inspected to MIL-STD-883 Method 2010 for visual defects.

What Limits the Detection Threshold of Copper(II)-Selective Fluorescent Probes Based on Thiazole-4-Carbaldehyde Hydrazones?

Quenching-based sensing of cupric ion in potable water using the condensation product of 2-(4-bromophenyl)-1,3-thiazole-4-carbaldehyde with thiosemicarbazide is governed primarily by the probe’s aggregation-induced self-quenching above 25 µM working concentration and by interference from ferric ion above a Fe³⁺/Cu²⁺ ratio of 1.2. The synthesis is carried out by refluxing the aldehyde (1.00 mmol) with thiosemicarbazide (1.02 mmol) in 30 mL of absolute ethanol containing 0.1% v/v glacial acetic acid for 2.5 h, after which the product precipitates upon cooling to 0 °C and is collected by vacuum filtration through a 10–16 µm porosity sintered glass funnel. The crude hydrazone is recrystallised from N,N-dimethylformamide/water (3:1 v/v) to reach 99.2% HPLC purity (UV detection at 254 nm, C18 column, acetonitrile/0.1% trifluoroacetic acid mobile phase). Method validation for the probe’s analytical application follows the linear calibration requirements of ISO 8466-1 (Water quality — Calibration and evaluation of analytical methods) with a five-point standard addition protocol over the range 0.05–2.00 mg/L Cu²⁺, and interlaboratory precision is assessed under ISO 5725-2 using a Horwitz-type reproducibility model. The formulated probe is supplied as a 10 µM stock solution in dimethyl sulfoxide packed in amber borosilicate ampoules under nitrogen blanketing, intended for use with a handheld fluorimeter configured for excitation at 365 nm and emission collection at 480 nm. The terminal commercial offering is a water quality field test kit comprising the probe ampoules, a pH 6.0 acetate buffer concentrate, and a portable LED-based fluorimeter calibrated from the factory with quinine sulfate dihydrate standard traceable to NIST SRM 936a.

Palladium Pincer Complex Precursors and Measured Catalytic Turnover Frequencies in Heck Arylation

The condensation of 2-(4-bromophenyl)-1,3-thiazole-4-carbaldehyde with 2,6-diisopropylaniline in dry toluene under Dean-Stark water removal produces the corresponding bis(imine) ligand that, upon direct orthopalladation with palladium(II) acetate in methanol at 50 °C for 24 h, yields an air-stable PCP-type pincer complex. The ligand formation step is driven with a 1.05:1 aldehyde-to-amine molar ratio, and the subsequent metalation proceeds at a Pd(OAc)₂ loading of 1.00 equivalent relative to the ligand. Catalytic performance is benchmarked against the coupling of 4-bromotoluene with styrene in N,N-dimethylacetamide using sodium acetate as base, where a catalyst loading of 0.1 mol% achieves full conversion within 2.0 h at 140 °C, corresponding to a turnover number (TON) of 970 and an average turnover frequency (TOF) of 485 h⁻¹. The complex is purified by flash chromatography on neutral alumina (Brockmann activity I) with dichloromethane/petroleum ether eluent, and its elemental composition is verified against the calculated values for C, H, N using ASTM D5291-16 (Standard Test Methods for Instrumental Determination of Carbon, Hydrogen, and Nitrogen in Petroleum Products and Lubricants, adapted for organometallics). Residual palladium in the purified catalyst precursor is quantified by inductively coupled plasma optical emission spectrometry according to ISO 11885:2007, with a target specification of ≥ 98.5% assay. The final product configuration is a 5-mL septum-capped vial containing 250 mg of the pre-catalyst powder, stored under argon in a 2–8 °C refrigerator, and commercialised as part of a cross-coupling screening kit that also includes an aryl bromide diversity set and a standard operating procedure aligned with the ACS Green Chemistry Institute Pharmaceutical Roundtable process mass intensity metric.

The route to anti-tubercular carbothioamide leads uses 2-(4-bromophenyl)-1,3-thiazole-4-carbaldehyde as the electrophilic carbon source in a one-pot oxidative amidation that installs the thiocarbonyl pharmacophore directly. The reaction vessel is charged with 1.0 equivalent of the aldehyde, 1.1 equivalents of 4-(trifluoromethoxy)benzylamine, 2.5 equivalents of elemental sulfur, and 1.5 equivalents of sodium sulfide nonahydrate in dimethylformamide, and the mixture is heated at 80 °C under a nitrogen atmosphere for 12 h. The thioamide product is precipitated by pouring the cooled reaction mass into 10 volumes of ice water, filtered, and recrystallised twice from acetonitrile/water (7:3 v/v) to reduce the residual sulfur content below 50 ppm. All process intermediates and final test articles intended for in vivo murine efficacy models are manufactured under a quality management system that follows the early-phase GMP recommendations of ICH Q7 Section 19 (APIs for Use in Clinical Trials), with particular attention to the control of mutagenic azide impurities when sodium azide is deployed as a leaving group in a preceding step; analytical testing complies with ICH M7(R1) and uses liquid chromatography hyphenated to high-resolution mass spectrometry for the detection of potentially genotoxic impurities at a threshold of 1.5 µg/day. In vitro activity of the resulting N-(4-(trifluoromethoxy)benzyl)-2-(4-bromophenyl)thiazole-4-carbothioamide is determined against Mycobacterium tuberculosis H37Rv using the microbroth dilution method referenced in CLSI M24-A2, with a measured minimum inhibitory concentration (MIC) of 0.25 µg/mL in the absence of serum protein binding. The terminal presentation is a lyophilised powder filled into 10-mL Type I borosilicate vials stoppered with bromobutyl rubber closures, shipped at −20 °C for integration into a preformulation screening programme aimed at developing an orally dispersible tablet with exposure surpassing the in-vitro-derived PK/PD target.

Suzuki Coupling Feedstock for Agricultural Carboxamide Fungicides

A structurally diverse library of thiazole-4-carboxamide fungicide candidates is assembled using 2-(4-bromophenyl)-1,3-thiazole-4-carbaldehyde as the common aryl bromide building block in an automated parallel synthesis platform. The compound is dissolved in anhydrous 1,4-dioxane at a concentration of 0.5 M and dispensed into 48-well reactor blocks pre-loaded with a mixture of Pd(OAc)₂ (1.0 mol%) and XPhos (2.5 mol%), along with 1.5 equivalents of the corresponding aryl boronic acid and 2.0 equivalents of K₃PO₄ as the base. The sealed vessels are heated to 100 °C with orbital shaking at 300 rpm for 8 h, after which the aldehyde group of the resulting biaryl intermediate is oxidised to the carboxylic acid using Jones reagent (CrO₃ in aqueous H₂SO₄) at 0 °C, followed immediately by amide coupling with substituted anilines via HATU/DIPEA in DMF. Each step is monitored by UPLC-MS with charged aerosol detection to quantify unreacted starting material. The entire synthesis campaign operates under the plant protection product regulatory framework specified in Regulation (EC) No 1107/2009, and individual compounds selected for field trial development are analysed according to the FAO specification guidelines for technical material ( 56/TK) including long-term storage stability at 54 ± 2 °C for 14 days. The downstream purification for compounds advancing to pilot scale consists of silica gel plug filtration with a 5% v/v methanol/dichloromethane eluent, followed by trituration with diisopropyl ether to remove triphenylphosphine oxide residues, resulting in isolated yields across the library that average 62% with a median purity of 97.8%. The finished active ingredient is standardised as a water-dispersible granule (WDG) formulation containing 50% w/w of the active substance, developed for the control of Rhizoctonia solani in turf and horticultural crops, and packaged in 25-kg fibre drums with polyethylene liners.