Refernces
10.1002/ejoc.201601364
The research presents a novel organocatalytic asymmetric sulfa-Michael addition reaction of 2-aminothiophenols to trans-chalcones, leading to the first enantioselective synthesis of 2,3,4,5-tetrahydro-1,5-benzothiazepines. These heterocyclic compounds are significant in medicinal chemistry and possess a variety of pharmacological properties. The study involved a meticulous optimization process to overcome challenges such as the instability of 2-aminothiophenols and the stereochemical instability of the intermediates during reductive amination. The reaction conditions were optimized using various bifunctional organocatalysts, with catalyst 3d showing the best performance. The solvent was also found to significantly influence the reaction, with 1,4-dioxane being optimal. The optimized protocol involved the use of degassed 1,4-dioxane and the addition of 2-aminothiophenol in solution to prevent dimerization and ensure reproducibility. The second step, reductive amination, was carefully investigated to prevent racemization, with conditions involving NaBH3CN and AcOH in methanol at 0°C proving effective. The scope of the reaction was tested with variously substituted trans-chalcones and 2-aminothiophenols, yielding the desired benzothiazepines in moderate to good yields and enantioselectivities. Analyses included 1H NMR, CSP-HPLC, and single-crystal X-Ray analysis to determine product purity, enantiomeric excess, and absolute configuration, respectively.
10.1039/c5ob02514a
The research focuses on the development of a palladium-catalyzed coupling reaction for the synthesis of N-aminosulfonamides, an important class of compounds found in natural products, pharmaceuticals, agrochemicals, and materials. The study utilizes aryl nonaflates, sulfur dioxide, and hydrazines as reactants in the presence of a palladium catalyst (Pd(OAc)2/XantPhos) and the phase-transfer catalyst TBAB in 1,4-dioxane at 80°C. The reaction scope was explored with various aryl nonaflates substituted with different functional groups, demonstrating good functional group tolerance and moderate to good yields. The experiments involved optimizing reaction conditions, such as catalyst choice, base, solvent, and temperature, to achieve the best yield of the desired N-aminosulfonamides. The analyses used to characterize the products included nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HRMS), which confirmed the structure and composition of the synthesized compounds.
10.1039/b802082e
The research focuses on the in situ generation of Mes2Mg as a non-nucleophilic carbon-centered base reagent for the efficient one-pot conversion of ketones to silyl enol ethers. The study utilizes commercially available MesMgBr and 1,4-dioxane to produce Mes2Mg reagent in situ, which then deprotonates ketones to yield trimethylsilyl enol ethers at accessible temperatures without nucleophilic addition. The experiments involved the optimization of reaction conditions, including the use of LiCl and 1,4-dioxane additives, to achieve high yields of silyl enol ether products with minimal side products. The analyses used to assess the conversion and purity of products included gas chromatography (GC), thin layer chromatography (TLC), infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and high-resolution mass spectrometry. The optimized one-pot procedure was demonstrated to be effective across a range of substrates and was also scalable to gram-scale reactions.
10.1002/asia.201000053
The research focuses on the design and synthesis of complex molecules from simple starting materials in a minimal number of steps, which is a significant challenge in organic synthesis. The study explores RhI-catalyzed two-component [(5+2)+1] cycloaddition reactions as an efficient method for constructing complex [5-8-5] and [6-8-5] ring systems, which are found in many natural products with significant biological activities. The researchers hypothesized that by modifying the substrates of the previously developed [(5+2)+1] cycloaddition with a five-membered carbocycle fused to the cyclopropane rings of ene-VCPs, they could achieve the synthesis of either a [5-8-5] tricyclic skeleton or a taxol skeleton in a single operation. The study used ene-VCPs and carbon monoxide (CO) as the primary reactants, with [Rh(CO)2Cl]2 as the catalyst, and 1,4-dioxane as the solvent. The results confirmed that the reaction proceeds via the cleavage of the external C-C bond of the cyclopropyl group, yielding a [5-8-5] ring system, and not the internal C-C bond, which would have led to a taxol skeleton. The method was found to be efficient for generating [5-8-5] systems with reasonable yields and has potential for the synthesis of natural products and their analogues with [5-8-5] skeletons.
10.1016/S0008-6215(00)90291-X
The study investigates the reaction of various 3-hetero-1,5-dialdehydes with tert-butyl cyanoacetate. The chemicals involved include thiodiglycolaldehyde and diglycolaldehyde, which react with tert-butyl cyanoacetate to yield derivatives of tetrahydrothiopyran and tetrahydropyran, respectively. Other dialdehydes with furan nuclei at the cy-position, such as a-(S)-(3-ethoxycarbonyl-2-methylfur-5-yl)diglycolaldehyde and a-(S)-(3-acetyl-2-methylfur-5-yl)diglycolaldehyde, produce D-xylo and L-arabino C-pyranosyl derivatives. Additionally, a-(S)-methoxy-a’-(R)-hydroxymethyldiglycolaldehyde leads to D-gluco and D-manno glycosides. The reactions are catalyzed by piperidine and carried out in aqueous 1,4-dioxane at room temperature. The products are isolated using column chromatography, and their structures are determined through elemental analysis and spectroscopic data. The study aims to synthesize 3-deoxy-C-glycosyl derivatives and 3-deoxyglycosides branched at C-3, with the relative proportions of products depending on the reaction time and molar ratios of the reactants.
10.1002/chem.202001439
The study presents a novel and practical method for ortho-selective C-H perfluoroalkylation, including trifluoromethylations, of anilines and indoles using ruthenium catalysis. The process is significant for the synthesis of various (per)fluoroalkylated building blocks, which are valuable for creating bioactive compounds and materials. The researchers utilized commercially available reagents RI and RfBr, achieving high site selectivity without the need for protecting groups. The methodology is attractive due to the availability and cost of the starting materials, and it offers a mild reaction condition for the direct C-H perfluoroalkylation of anilines. The study also explores the substrate scope and reaction conditions, demonstrating the potential for gram-scale synthesis and the successful application to indoles, providing a pathway to selectively functionalize these important heterocyclic compounds.
10.1016/j.bmc.2014.05.014
The study focuses on the enzymatic preparation and resolution of cis and trans-3-amino-4-hydroxytetrahydrofurans and cis-3-amino-4-hydroxypyrrolidines, which are important heterocyclic amino alcohols found in bioactive natural products and drugs. The researchers utilized Candida antarctica lipases A and B as catalysts in hydrolytic processes to achieve high enantioselectivity for these heterocycles. The study successfully assigned the absolute configurations of the optically pure heterocycles obtained and demonstrated a convenient biocatalytic approach for preparing all isomers of these compounds. The findings have implications for the synthesis of complex molecules with potential biological activities, as well as for applications in organocatalysis and as chiral auxiliaries.
10.1016/j.tetlet.2010.08.110
The research focuses on the synthesis and characterization of a novel heterocyclic compound, thiazolo[4,5-d]thiazole, and its derivatives for potential optoelectronic applications. The synthesis involved a six-step process starting from butane-2,3-dione, leading to the formation of 2,5-dimethylthiazolo[4,5-d]thiazole and its methylation to produce 2,3,5-trimethyl thiazolothiazolium iodide. Key reactants included PCl5, Lawesson’s reagent, and potassium ferricyanide, with various solvents like 1,4-dioxane and THF used to optimize reaction conditions. Analytical techniques such as NMR spectroscopy, IR spectroscopy, and UV-Vis spectroscopy were employed to confirm the structures and evaluate the optical properties of the synthesized compounds, demonstrating their potential as nonlinear optical materials.
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