10.3987/COM-88-4594
The research investigates the synthesis and reactivity of a series of N-substituted 4-amino-2(5H)-furanones derived from β-tetronic acid. The purpose of the study is to explore the Eschenmoser-Mannich reaction of these furanones, which has not been extensively examined previously, and to understand their potential for α-homologation and use as building blocks for heterocyclic compounds. The researchers synthesized various N-substituted 4-amino-2(5H)-furanones by reacting β-tetronic acid with different aliphatic and aromatic amines. These compounds were then subjected to the Eschenmoser-Mannich reaction, yielding corresponding Mannich bases quantitatively. The study concludes that the 4-amino-2(5H)-furanones exhibit improved reactivity at position 3, as evidenced by their electrophilic substitution reactions and the formation of Mannich bases. The researchers also explored the quaternization of these Mannich bases with methyl iodide, observing the formation of normal and intermolecular quaternary salts, particularly in the case of the 4-anilinofuranone system. The chemicals used in the process include β-tetronic acid, various amines (such as dimethylamine, methylamine, benzylamine, and aniline), Eschenmoser's salt, methyl iodide, and other reagents like potassium carbonate and sodium borohydride for different steps of the synthesis and reactions.
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.tetlet.2013.01.021
The research focuses on the solventless, convenient synthesis of new cyano-2-aminopyridine derivatives from enaminonitriles using microwave irradiation. The purpose of this study was to develop a green approach to synthesize 4-substituted-3-cyano-2-aminopyridines, which are important intermediates in organic synthesis and exhibit various biological properties. The methodology is highlighted for its ease of execution, rapid access, and good yields. The chemicals used in the process include various primary amines such as methylamine, allylamine, butylamine, isopropylamine, and benzylamine, which reacted with enaminonitriles to form the desired 2-aminopyridine derivatives. The study concluded that the solvent-free methods, particularly under microwave activation, were efficient and preferred due to shorter reaction times and higher yields, thus opening a new route for the synthesis of various substituted nitrogen heterocycles.
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