10.1039/c3ra41850b
The research presents a novel method for C-C bond formation between tertiary amines and carbon nucleophiles using molecular iodine as a catalyst, molecular oxygen as the terminal oxidant, and visible light irradiation. The study explores cross-dehydrogenative coupling (CDC) reactions, which are advantageous as they do not require preactivation of precursors. The experiments involved using N-phenyl tetrahydroisoquinoline as a test substrate with nitromethane, and various iodine sources and solvents were tested to optimize the reaction conditions. The best results were obtained using acetonitrile (MeCN) as the solvent and iodine (I2) as the catalyst. The reaction was carried out under an oxygen balloon, with a 22 W fluorescent lamp providing the visible light irradiation. Control experiments confirmed the necessity of molecular iodine, molecular oxygen, and light for the reaction to proceed. The scope of the reaction was further demonstrated with different substrates and carbon nucleophiles, yielding products such as aza-Henry and Mannich products. The reaction mechanism was also investigated, suggesting the formation of iminium ions by oxidation of tertiary amines, followed by acid-promoted addition of the carbon nucleophile.
10.3762/bjoc.8.95
The research presents an in-depth study on the application of two-directional synthesis in diversity-oriented synthesis (DOS), focusing on the rapid construction of complex molecular architectures from simple starting materials, particularly for the synthesis of alkaloid scaffolds. The experiments involved the synthesis of linear precursors, such as N-Boc-aminoalkenes containing α,β-unsaturated ester groups, which were then subjected to intramolecular pairing reactions under various Lewis acid conditions to form bicyclic and tricyclic scaffolds. Reactants included compounds like nitromethane and tris(hydroxymethyl)aminomethane (Tris), and analyses utilized techniques such as NMR spectroscopy, X-ray crystallography, and IR spectroscopy to confirm the structures and stereochemistry of the synthesized compounds. The study also explored the total synthesis of myrrhine and the potential of different substrates like nitromethane and Tris in DOS, demonstrating the versatility and efficiency of two-directional synthesis in generating molecular diversity.
10.1002/anie.200802515
The research investigates the cooperative catalysis of primary and tertiary amines immobilized on oxide surfaces for one-pot carbon-carbon bond-forming reactions. The purpose is to develop an efficient heterogeneous catalyst for organic C-C bond-forming reactions by combining both primary and tertiary amines on the same solid surface to activate both nucleophiles and electrophiles. The key chemicals used include benzaldehyde, nitromethane, silica-alumina (SA), 3-aminopropyltriethoxysilane, and 3-(diethylamino)propyltrimethoxysilane. The study found that the double-amine catalysts immobilized on silica-alumina (SA–NH2–NEt2) showed high initial conversion rates and selectivity for the synthesis of 1,3-dinitroalkanes compared to other amine catalysts and homogeneous mixtures. The presence of surface acid sites on the silica-alumina support enhanced the cooperative catalysis, and the catalyst was effective for one-pot reaction sequences. The research concludes that the SA–NH2–NEt2 catalyst is highly active for the production of 1,3-dinitroalkanes due to its multifunctional surface, which enables both acceleration of single reactions and promotion of one-pot reaction sequences.
10.1002/chem.201502129
The research focuses on the development of a novel C2-symmetric Schiff-base ligand derived from tridentate-Schiff-base, which is applied to the asymmetric Michael addition of nitroalkanes to 2-enoyl-pyridine N-oxides. This ligand, when combined with scandium(III) or copper(II) complexes, catalyzes the reaction with unprecedented levels of diastereoselectivity and enantioselectivity. The study explores the reaction using various nitroalkanes and 2-enoyl-pyridine N-oxides, achieving high yields and stereoselectivities. The researchers also demonstrate the synthetic utility of this method by converting the optically active adduct to a biologically active dihydro-2H-pyrrol 4a, an analogue of nicotine. Analyses include the determination of yields, enantiomeric excess (ee) by HPLC on a chiral stationary phase, and diastereomeric ratios (d.r.) by 1H NMR spectroscopy. The research also investigates the reaction mechanism, revealing a negative nonlinear effect in the catalysis by scandium, and proposes a transition-state model based on spectroscopic experiments and product configuration analysis.
10.1002/poc.435
The research focuses on the tautomeric preferences of 2-phenylhydrazones of 1,3-diphenyl-1,2,3-trione in chloroform solution, as detected by 15N NMR chemical shifts. The study aims to understand whether the substituent in the phenylhydrazone moiety influences the tautomeric preference and the transmission of the substituent effect within the molecules. Experiments involved the synthesis of compounds through the coupling of benzenediazonium ion to 1,3-diphenyl-1,3-propanedione, followed by purification via recrystallization from ethanol. The synthesized compounds were then analyzed using 1H, 13C, and 15N NMR spectroscopy, with chemical shifts referenced to tetramethylsilane (TMS) and nitromethane. Additionally, ab initio calculations at the HF/B3LYP level of theory with GIAO-HF/DFT method were conducted to calculate the chemical shifts of carbon atoms, and X-ray crystallography was used to detect the tautomer in the crystal state. The study found that the ketohydrazone tautomer is significantly favored over its proton-transfer products, and this tautomer was also detected in the crystalline state, indicating that the additional carbonyl group or substituent does not affect the tautomeric and configurational preferences.
10.1055/s-1982-30055
The research details an improved procedure for the Michael reaction of chalcones, a valuable C-C bond forming reaction commonly catalyzed by alkali metal hydroxides or alkoxides. The study aimed to achieve better results using weaker bases such as piperidine, tertiary amines, or quaternary ammonium hydroxides. The researchers found that partially dehydrated commercial barium hydroxide efficiently catalyzed Michael reactions of chalcones with active methylene compounds like ethyl malonate, ethyl acetoacetate, acetylacetone, nitromethane, and enolizable ketones such as cyclohexanone and acetophenone. The process involved stirring the components in ethanol at reflux or room temperature, yielding products with sharp melting points and single spots on T.L.C., and spectra that matched those of recrystallized products. The yields were generally higher than reported yields or at least of the same order, and the method was operationally simpler compared to other basic catalysts. The study concluded that while the barium hydroxide catalyst was cheap and easily prepared, its catalytic activity decreased over time when exposed to moist air, and the use of solvents other than ethanol or methanol led to poorer yields.
10.1016/j.tetlet.2013.05.019
The study investigates the highly enantioselective conjugate addition of nitroalkanes to enones catalyzed by cinchona alkaloid-derived primary amine. The researchers used various cinchona alkaloid-derived catalysts and cyclohexane diamine-derived bifunctional catalysts to promote the asymmetric Michael addition reaction of 4-phenylbut-3-en-2-one (2a) with nitromethane (3a). Among them, quinine amine 1i showed the most promising results, achieving good yield and high enantiocontrol. The optimized reaction conditions were explored, with THF as the solvent yielding the best results. The scope of the addition of nitroalkanes to enones was then investigated, revealing that the catalyst 1i could efficiently catalyze the conjugate addition of nitromethane to various enones, affording the desired products with excellent enantioselectivities. The study expanded the domain of organocatalyzed enantioselective conjugate addition process of nitroalkanes to enones.
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