10.1021/ol0502026
The study by Scott T. Handy and Duncan Omune investigates the reductive cyclization of tethered bis-enones with one-carbon tethers, focusing on the influence of reaction conditions and α-substitution on the cyclization pathway. They found that the cyclization products, either pinacol or hydrodimerization-type, are highly dependent on these factors. The researchers synthesized three cyclization substrates and explored their reductive cyclization under electrochemical conditions and using samarium diiodide. They observed that electrochemical conditions favored pinacol-type products, while samarium diiodide favored reductive cyclization products. The study suggests that chelation and steric effects play a crucial role in determining the cyclization pathway, with Lewis acidic metals promoting pinacol formation and non-chelatable metals favoring reductive cyclization. This mechanistic understanding was further supported by experiments using magnesium in methanol, which resulted in pinacol products. The findings highlight the importance of reaction conditions in controlling the cyclization outcome and provide insights into the mechanism of reductive cyclization reactions.
10.1007/s11172-009-0199-8
The research focuses on the Mannich reaction in the synthesis of N,S-containing heterocycles, specifically the recyclization of stable cyclic Michael adducts, N-methylmorpholinium 6-R-6-hydroxy-1,4,5,6-tetrahydropyridine-2-thiolates, to pyrimido[4,3-b][1,3,5]thiadiazines under aminomethylation reaction conditions. The experiments involve the reaction of 5-substituted N-methylmorpholinium 4-aryl-6-R-3-cyano-6-hydroxy-1,4,5,6-tetrahydro-pyridine-2-thiolates with primary amines and formaldehyde (HCHO) in ethanol, leading to the formation of 3,7-disubstituted 8-aryl-3,4,7,8-tetrahydro-2H,6H-pyrimido[4,3-b][1,3,5]thiadiazine-9-carbonitriles in low yields (5—28%). The reactants include cyanothioacetamide, aromatic aldehydes, primary amines, and HCHO. The analyses used to characterize the products include infrared (IR) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy, and elemental analysis, which confirmed the structures of the synthesized pyrimido[4,3-b][1,3,5]thiadiazines.
10.1039/c4dt00658e
The research investigates the unique reactivity of a zirconacycle compound, Cp2Zr{κ2-N(SiHMe2)SiHMeCH2} (1), with a focus on its direct hydrosilylation reaction with formaldehyde. The purpose of the study was to explore the reactions of this compound with a series of nucleophilic and electrophilic agents, as well as its behavior with carbonyls, to develop a rationale for the unexpected hydrosilylation activity. The conclusions drawn from the research indicate that the compound 1, despite containing classical 2-center-2-electron SiH groups, reacts with formaldehyde at the exocyclic SiH to form a methoxysilyl group, a transformation that diverges from the reactions of β-H free analogs. This reactivity is attributed to the metallacyclic structure of 1, which may enhance the reactivity of the exocyclic β-hydrogen or limit non-classical interactions that would otherwise stabilize the reactive β-hydrogen. Key chemicals used in the process include formaldehyde, carbon monoxide, tris(perfluorophenyl)borane (B(C6F5)3), and various donor ligands such as OPEt3, PMe3, pyridine, and DMAP.
10.1002/ejic.200300617
The research presented focuses on the synthesis and study of aminomethyl and aminoacetyl complexes of palladium(II), platinum(II), iron(II), and rhenium(I) with N-phthaloyl as an amino protecting group. The study also delves into the mechanistic aspects of palladium-catalyzed amidocarbonylation, a process for forming a-amino acids from aldehydes, amides, and carbon monoxide. The researchers synthesized new complexes through oxidative addition reactions using various metal carbonyls and organic halides, yielding compounds such as [Re{C(O)CH2N-phthaloyl}(CO)5], [FeCp(CH2N-phthaloyl)(CO)2], [FeCp{C(O)CH2N-phthaloyl}(CO)2], trans-[PdBr(CH2N-phthaloyl)(PPh3)2], and trans-[Pd{C(O)CH2N-phthaloyl}(X)(PPh3)2], among others. They performed ligand exchange reactions to obtain bis(phosphane) complexes and cationic chelate complexes through halide abstraction. The structures of several compounds were confirmed via single-crystal X-ray analysis. To investigate the mechanism of the palladium-catalyzed amidocarbonylation, they utilized a model system consisting of phthalimide, formaldehyde, and carbon monoxide, which led to the formation of N-phthaloylglycine. The study employed various analytical techniques, including infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy, to characterize the synthesized complexes and monitor the reaction progress. The results provided insights into the elementary steps of the catalytic cycle and confirmed the proposed mechanism for the amidocarbonylation process.
10.1021/ja029059r
The research focuses on elucidating the supramolecular structure of benzoxazine oligomers using a combination of molecular modeling, density functional theory (DFT) calculations, and advanced solid-state nuclear magnetic resonance (NMR) experiments. The study characterizes intramolecular hydrogen bonds as the driving forces behind the ring-shaped and helical conformations observed in trimeric and tetrameric units. The experiments involved the synthesis of model trimer and tetramer structures, which were then subjected to fast magic-angle spinning (MAS) 1H NMR spectra to assign resonances of protons forming hydrogen bonds. The experiments use n-hexane, acetone, chloroform, methylamine, p-cresol, and formaldehyde as solvents and reagents. DFT-based geometry optimizations and 1H chemical-shift calculations were used to validate and refine the structural models. Additional analyses included homonuclear 1H-1H double-quantum NMR spectra to identify local proton-proton proximities and quantitative 15N-1H distance measurements obtained from dipolar spinning sideband patterns. These experimental and computational approaches collectively supported the proposed helical geometry of the benzoxazine polymer, which could account for the material's unique chemical properties.
10.1016/j.ejmech.2007.02.019
The research focused on synthesizing a series of 12 new Mannich bases derived from 6-(3-aryl-2-propenoyl)-2(3H)-benzoxazolones, aimed at evaluating their potential as antineoplastic agents. The study utilized chemicals such as acetyl chloride, aluminum chloride, dimethylformamide (DMF), formaldehyde, and various secondary amines in the synthesis process. The cytotoxicity of the synthesized compounds was assessed using the MTT assay on human pre-B-cell leukemia cell line BV-173 and chronic myeloid leukemia cell line K-562. The results indicated that the Mannich bases exhibited concentration-dependent cytotoxic effects, with some compounds inducing programmed cell death at low micromolar concentrations. The findings suggest that these heterocyclic chalcones represent a promising class of cytotoxic agents, warranting further pharmacological evaluation to elucidate their mechanisms of action and structure-activity relationships.
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.
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