10.1002/cctc.201500053
The study presented in the PDF document titled "Dual [Fe+Phosphine] Catalysis: Application in Catalytic Wittig Olefination" focuses on the development and application of a dual catalysis system involving iron hydride complexes and phosphines for the selective reduction of carbonyl and phosphine oxide groups. The researchers explored the use of Fe-based complexes for the hydrosilylation of aldehydes, ketones, and phosphine oxides, demonstrating that these complexes could effectively reduce phosphine oxides to phosphines. This reduction process was then integrated into a catalytic Wittig olefination reaction, which is a synthetically useful transformation for the formation of olefins from aldehydes or ketones and a-halocarboxylic acid esters. The study successfully utilized a readily accessible Fe-H complex in conjunction with triphenylphosphine as an organocatalyst and phenylsilane as a stoichiometric reductant, achieving moderate to good yields of the desired olefination products. This work not only expands the application scope of Fe-based catalysis but also provides a potential avenue for the in situ recycling of phosphines, which is beneficial for large-scale applications and more sustainable chemical processes.
10.1016/S0040-4039(00)00097-6
The study focuses on the photocyclization and photooxidation processes of 3-styrylthiophene, a compound with two isomers: trans-3-styrylthiophene (1) and cis-3-styrylthiophene (2). The research investigates how these isomers react under different photochemical conditions, including in nonpolar and polar solvents, with and without sensitizers. The key findings include that cis-3-styrylthiophene (2) undergoes photochemical cis–trans isomerization and cyclization to form dihydronaphtho-[1,2-b]thiophene (3), with a higher quantum efficiency in nonpolar solvents. Dye-sensitized photooxidation of 3-styrylthiophene results in the production of benzaldehyde and 3-thiophenecarboxaldehyde, and the process is suggested to occur via a superoxide radical anion pathway rather than through singlet oxygen. Additionally, auto-photooxidation in the presence of oxygen leads to photocyclization, oxidation, and dimerization products. The study proposes that these reactions may involve the formation of a charge transfer complex between oxygen and the substrate. The research is significant for understanding the behavior of polythiophenes, which are important for the production of conductive polymers, and could contribute to improving the photostability of these materials.
10.1021/jo802371z
The research focuses on the dual stereoselectivity in the dialkylzinc reaction using (-)-α-pinene derived amino alcohol chiral auxiliaries. The study involves the synthesis of two regioisomeric amino alcohols, 3-MAP and 2-MAP, from (+)-nopinone, which is prepared from naturally occurring (-)-α-pinene. These amino alcohols serve as chiral auxiliaries in the addition of diethylzinc to benzaldehyde, yielding secondary alcohols with high enantiomeric excess (ee). The experiments utilize various reactants, including (+)-nopinone, lithium aluminum hydride, and diethylzinc, and employ techniques such as X-ray crystallography, two-dimensional NMR, and NOE correlations for characterization and confirmation of stereochemistry. The research also explores the use of these amino alcohols in the dimethylzinc addition reaction and provides mechanistic insights into the observed dual stereoselectivity. The analyses include chiral gas chromatography to determine the enantiomeric excess and optical rotation to assign the absolute configuration of the products.
10.1002/ejoc.201200180
The research focuses on the synthesis of (E)-4-aryl-1,1,1-trifluoro-3-tosylbut-3-en-2-ones, which are fluorinated building blocks, and their application in the highly stereoselective preparation of trans-2,3-dihydrofurans substituted with trifluoromethyl and sulfonyl groups. The experiments involved a two-step process to prepare the fluorinated building blocks, followed by their reaction with arsonium bromides in the presence of Cs2CO3 in CH2Cl2 at reflux conditions, leading to the formation of 4-tosyl-5-trifluoromethyl-trans-2,3-dihydrofurans with good to excellent yields. The reactants included 1-bromo-3,3,3-trifluoropropan-2one, sodium p-toluenesulfinate, aromatic aldehydes, and various arsonium bromides. The analyses used to characterize the synthesized compounds comprised 1H NMR, 13C NMR, 19F NMR, IR spectroscopy, mass spectrometry, and elemental analysis, with X-ray diffraction analysis employed for certain compounds to confirm their stereochemistry.
10.1246/cl.1992.535
The research focused on the unusual reaction of chalcone derivatives with aromatic aldehydes, promoted by ytterbium metal. The purpose of the study was to investigate the cyclodimerization of chalcone derivatives and the role of ytterbium metal in promoting the reaction, which led to the formation of cyclopentanols or cyclopentanones. The researchers observed that the reaction yielded different products depending on the amount of aldehyde used: with an equimolar amount of benzaldehyde, they obtained 2-benzoyl-5-phenylhydroxymethyl-1,3,4-triphenylcyclopentanol, while an excess of aldehyde resulted in 2,5-bis(benzoyl)cyclopentanol. Key chemicals used in the process included chalcone, benzaldehyde, anisaldehyde, and ytterbium metal, with solvents like THF-HMPA employed in the reactions. The conclusions drawn from the study indicated that the cyclodimerization of chalcone derivatives promoted by ytterbium metal involves dianion species, with the negative charge unexpectedly distributed on oxygen and carbon-5 of the cyclopentanol rings, leading to the selective formation of products at the C-5 position.
10.1080/00397910802241407
The research presents the synthesis and characterization of a new series of hydroxy pyrazolines, which are nitrogen-containing heterocyclic compounds known for their broad spectrum of biological activities such as antitumor, immunosuppressive, antibacterial, anti-inflammatory, anticancer, antidiabetic, and antidepressant properties. The study begins with the preparation of 3-phenyl-1-(thiophen-2-yl)prop-2-en-1-one (chalcone 1) through the Claisen-Schmidt condensation of 2-acetyl thiophene with benzaldehyde. This chalcone 1 is then converted into 2,3-dibromo-3-phenyl-1-(thiophen-2-yl)propan-1-one (chalcone dibromide 2) by reacting with bromine in chloroform. Further reaction of chalcone dibromide 2 with various thiosemicarbazides in the presence of triethylamine in absolute ethanol yields hydroxy pyrazolines 3a–h. The synthesized compounds are characterized using IR, 1H NMR, and 13C NMR spectroscopy, with their purity confirmed by elemental analysis. The research also includes the preparation of substituted thiosemicarbazides used in the reaction, and the detailed experimental procedures for the synthesis of each compound are provided in the article.
10.1016/j.jorganchem.2009.02.018
The research focuses on the catalytic hydrogenation of C@O and C@N bonds using rhodium and iridium thiolate complexes that facilitate the heterolysis of H2. The study investigates the catalytic activity of coordinatively unsaturated rhodium and iridium complexes, Cp*M(PMe3)(SDmp) (1a: M = Rh; 1b: M = Ir), in the hydrogenation of benzaldehyde, N-benzylideneaniline, and cyclohexanone under mild conditions at low temperatures and 1 atm of H2. The key reactants include the metal complexes 1a and 1b, benzaldehyde, N-benzylideneaniline, and cyclohexanone. The experiments involved the generation of M–H/S–H complexes Cp*M(PMe3)(H)(HSDmp) (2a: M = Rh; 2b: M = Ir) through H2 heterolysis by 1a or 1b, which were proposed to transfer both M–H hydride and S–H proton to the substrates. The catalytic reactions were终止 by the dissociation of H-SDmp from the metal centers of 2a and 2b. The analyses used to monitor the reactions and characterize the products included 1H, 13C{1H}, and 31P{1H} NMR spectroscopy, infrared spectroscopy, ESI-MS spectrometry, and elemental analysis. The structure of one of the complexes formed during the reaction was confirmed by X-ray diffraction analysis.
10.1021/jm00388a007
The research focuses on the synthesis and evaluation of a series of (3-phenylflavonoxy)propanolamines, with the aim of identifying potential antihypertensive agents that do not exhibit β-adrenergic receptor blocking activity. The study was motivated by the desire to develop a class of agents with both β-adrenoceptor antagonist and vasodilatory properties, potentially offering more effective treatment for hypertension. The researchers synthesized various compounds and tested them for their ability to lower systolic blood pressure in spontaneously hypertensive rats and for their affinity to β-adrenergic receptors. The conclusion was that some compounds in the series, particularly those with an n-propyl or cyclopropyl substitution, showed effective antihypertensive properties without antagonizing β-adrenergic receptors. The chemicals used in the synthesis process included benzylamine, formaldehyde, benzaldehyde, 2-phenethylamine, and various substituted amines, among others. The study highlighted the unique structure-activity relationships of these compounds, which, despite their structural similarities to classical β-blockers, did not exhibit β-antagonist properties but were still effective as antihypertensive agents.
10.1002/anie.201107407
The research explores a highly enantioselective catalytic method for synthesizing homopropargylic alcohols, which are valuable intermediates for cross-coupling, metathesis, and heterocycle synthesis. The study aims to address the challenges of lower reactivity and regioselectivity control associated with enantioselective propargylation reactions. The researchers used benzaldehyde and allenyl boronic acid pinacol ester as key reactants, with chiral phosphoric acid (PA5) as the catalyst. The reaction was optimized in toluene at low temperatures (-20°C) to achieve high enantioselectivity (up to 91% ee). The methodology was extended to various aldehydes, yielding excellent results. Computational studies revealed that the catalyst forms a strong hydrogen bond with the pseudo-equatorial oxygen of the allenyl boronate, and the high enantioselectivity is due to steric interactions between the catalyst and the boronate. The findings demonstrate a simple, efficient, and broadly applicable method for synthesizing chiral homopropargylic alcohols, with potential applications in the synthesis of biologically active compounds.
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