10.1002/chem.201805631
The research presented in the scholarly article "Isothiourea-Catalyzed Regioselective Acylative Kinetic Resolution of Axially Chiral Biaryl Diols" by Shen Qu, Mark Greenhalgh, and Andrew Smith, focuses on the development of a kinetic resolution method for the synthesis of axially chiral biaryl diols using isothiourea as a catalyst. The study investigates the reaction scope and limitations, and it identifies that the presence of two hydroxyl groups in the substrate is crucial for achieving good conversion and high selectivity. The research utilizes various isothiourea catalysts, solvents, and anhydrides to optimize the reaction conditions. Key findings include the necessity of a mixed anhydride (2,2-diphenylacetic pivalic anhydride) for high selectivity and the discovery that substrates with 3,3'-substituents hinder effective acylation. The optimized method showcases high enantioselectivity (s values up to 190) and is applied to a range of binaphthyl and biphenyl diols. The experiments involve the use of chiral HPLC for the determination of enantiomeric ratios (er) and 1H NMR spectroscopic analysis for assessing conversion and product ratios. The research also explores the regioselective acylative kinetic resolution of unsymmetrical biaryl diol substrates and proposes acylation transition state models to explain the observed atropselectivity.
10.1016/S0040-4039(01)01178-9
The research focuses on the synthesis of 5-(ω-sulfhydrylalkyl)salicylaldehydes, which are precursors for the preparation of alkanethiol-modified metal salens. These compounds are of interest for their potential use in modifying the surfaces of gold electrodes. The experiments involved multistep syntheses to obtain two specific alkanethiol-modified salicylaldehydes: 5-(2-sulfhydrylethyl)salicylaldehyde and 5-(6-sulfhydrylhexyl)salicylaldehyde. Key reactants included 4-methoxyphenethyl alcohol, hydriodic acid, Grignard reagent, paraformaldehyde, triethylamine, and thiourea, among others. The synthesis procedures involved refluxing, formation of Grignard reagents, column chromatography for purification, and treatment with base. The synthesized compounds were characterized using gas chromatography-mass spectrometry (GC–MS) and nuclear magnetic resonance (NMR) spectrometry to confirm their structures and purity.
10.1038/nchem.1039
The research focuses on the development of an organocatalytic asymmetric domino Michael-aldol reaction for the construction of bispirooxindoles containing three quaternary stereocenters. The experiments involve the reaction between 3-substituted oxindoles and methyleneindolinones, catalyzed by a novel multifunctional organocatalyst that includes tertiary and primary amines and thiourea moieties. This catalyst activates substrates simultaneously, providing high levels of stereocontrol over four stereocenters. The analyses used to evaluate the reactions include isolated yields, diastereoselectivity (d.r.), and enantioselectivity (e.r.), which were determined by crude 1H-NMR spectroscopy, chiral-phase HPLC, and in some cases, X-ray crystallographic analysis to determine the absolute configurations of the products.
10.1515/znb-2011-0512
The research focuses on the synthesis and anti-HIV activity of novel substituted thiazol-2-ylidene-benzamides and their reaction with 1-aza-2-azoniaallene salts. The study involves the preparation of a series of N-(3-(substituted-alkyl- or halophenyl)-4-methylthiazol-2(3H)-ylidene)-substituted alkyl- or halo-benzamides through base-catalyzed cyclization of corresponding 1-(substituted-alkyl- or halo-benzoyl)-3-(substituted-halophenyl)thioureas. Additionally, substituted pyrazolo[4,3-d]thiazol-5(6aH)-ylidene)benzamides were synthesized via cycloaddition with reactive cumulene intermediates. The synthesized compounds were evaluated for their antiviral activity against HIV-1 and HIV-2 replication in MT-4 cells. The experiments utilized various analytical techniques, including 1H and 13C NMR, IR, and mass spectrometry, to characterize the structures of the synthesized compounds. The study identified compounds 35 and 39 as potential non-nucleoside reverse transcriptase inhibitors (NNRTIs) with significant activity against HIV-2.
10.1039/b404706k
The study focuses on the design, synthesis, and photophysical evaluation of four fluorescent photoinduced electron transfer (PET) chemosensors (1–4) for anion detection. These chemosensors are based on a simple design that utilizes charge-neutral aliphatic or aromatic thiourea anion receptors connected to an anthracene fluorophore via a methylene spacer. The anion recognition occurs through 1:1 hydrogen bonding between the thiourea protons and the anion, as demonstrated by changes in 1H NMR in DMSO-d6. The sensors were designed for detecting anions such as fluoride, acetate, phosphate, and for the recognition of N-protected amino acids. The purpose of these chemicals is to serve as PET sensors that quench fluorescence emission upon anion recognition due to enhanced efficiency of electron transfer quenching from the receptor to the excited state of the fluorophore. This allows for the modulation of the acidity of the thiourea receptor moiety by varying the nature of the thiourea substituent, thereby altering the sensitivity of anion recognition.
10.1021/jo500710g
The study focuses on the development and application of thiourea-based fluorescent chemosensors for the detection of aqueous metal ions and cellular imaging. The researchers made significant advances in understanding the coordination environment of thioureas, developed a new generation of chemosensors with higher affinities for Zn2+ and Cd2+, and demonstrated the use of a thiourea-based chemosensor for fluorescence microscopy imaging of Hg2+ ion concentrations in living mammalian cells. Key chemicals used in the study include thioureas, naphthalimide chromophores, metal ions (Zn2+, Cd2+, Hg2+, Pb2+), and fluorescent chemosensors MePic and DiPic. These chemicals served to create a fluorescence response upon association with metal ions, allowing for sensitive detection and imaging of these ions in aqueous environments and cellular systems.
10.1016/j.carres.2011.11.006
The research aims to synthesize novel compounds that are linked to sugars and possess both antioxidant properties and the ability to inhibit acetylcholinesterase, an enzyme associated with Alzheimer's disease. The study compares the efficiency of conventional heating methods with microwave-assisted synthesis for the creation of these compounds, which include oxo-/thioxopyrimidines and tetrazoles linked to furanoses with D-xylo and D-ribo configurations, and to a D-galacto pyranose. The chemicals used in the synthesis process involve dialdofuranoses and dialdopyranoses, β-keto esters, urea or thiourea, hydroxylamine hydrochloride, copper sulfate, triethylamine, dicyclohexylcarbodiimide, and sodium azide. The research concludes that microwave irradiation is a more efficient method, yielding the target molecules in high yield and in a significantly shorter time (10 minutes) compared to conventional heating. The synthesized compounds showed acetylcholinesterase inhibition ranging from 20% to 80% at a concentration of 100 μg/mL and exhibited antioxidant activity in the β-carotene/linoleic acid assay, with some compounds showing IC50 values comparable to gallic acid. Importantly, the bioactive compounds did not exhibit cytotoxic effects on human lymphocytes nor genotoxicity, indicating their potential as non-toxic therapeutic agents for the control of Alzheimer's disease symptoms.
10.1002/cctc.202001099
The study presents a novel synthetic strategy for the formation of aryl amides from thioureas and arylboronic acids, utilizing palladium-catalyzed desulfurative coupling, which involves a Suzuki?Miyaura coupling reaction. The key chemicals used in this research include thioureas, arylboronic acids, a palladium catalyst, and silver salts. Thiourea serves as a precursor for the formation of acyclic diaminocarbene (ADC) complexes, which are generated in situ with the help of silver salts. These complexes are crucial for the coupling reaction with arylboronic acids, leading to the synthesis of aryl amides upon further hydrolysis. Silver salts play a dual role: they facilitate the desulfurization process to form ADC-metal complexes and act as oxidants to regenerate PdII from Pd0, thus sustaining the catalytic cycle. This method enriches the application of thiourea chemistry and expands the scope of the Suzuki?Miyaura coupling, providing an efficient and green approach to amide synthesis.
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