RESUMEN
We herein report the acid/base-steered two distinct reaction pathways of 2-acylbenzoic acids with isatoic anhydrides. In the presence of Na2CO3, the cascade process consists of the cyclization of 2-acetylbenzoic acid and nucleophilic ring-opening reaction of isatoic anhydride to furnish isobenzofuranone derivatives with high efficiency. However, p-toluenesulfonic acid can promote the product isobenzofuranones to undergo sequential intramolecular rearrangment, nucleophilic addition and cyclization reaction to produce diverse isoindolobenzoxazinones in good yields. The synthetic utility of this method was further demonstrated by the gram-scale preparation of the desired products and the facile transformations of the resulting products.
RESUMEN
This review describes recent advances in copper-catalyzed difluoroalkylation reactions. The RCF2 radical is generally proposed in the mechanism of these reactions. At present, various types of copper-catalyzed difluoroalkylation reactions have been realized. According to their characteristics, we classify these difluoroalkylation reactions into three types.
Asunto(s)
Cobre , Ciclización , Catálisis , Estructura MolecularRESUMEN
An exquisite protocol to the synthesis of erythrina-related structural derivatives was developed, which is composed of a nucleophilic addition of tertiary enamides to ketonic carbonyls and the trapping of acyliminium by an aromatic unit. This protocol afforded a powerful method for the construction of diverse fused N-pentacyclic skeletons in high efficiency and excellent diastereoselectivity by just using different acid catalysts.
RESUMEN
Based on the properties of oppositely charged natural polysaccharides, the polyelectrolyte complexes (PECs) prepared with chitosan-related polycationic polyelectrolytes and cellulose-related polyanionic polyelectrolytes have been widely concerned for their potential applications as micro-drug-carriers for colon. However, the poor mechanical property of the PECs becomes the obstacle encountered in practical applications. This study investigated the effect of the cross-linking agent (sodium polyphosphate, PPS) on the performances of sodium cellulose sulfate -chitosan/water soluble chitosan (NaCS-CS/WSC) microcapsules. The results revealed that PPS could penetrate through the PEC film and form tighter interior structures compared with the microcapsules without the addition of cross-linking agent. The NaCS-CS microcapsules and NaCS-WSC microcapsules with or without PPS had distinct microstructures, which could be ascribed to the different physicochemical properties of CS and WSC. During the formation process, CS can be dissolved in water under acidic conditions, while WSC can be directly dissolved and protonated in acid-free aqueous providing NH3(+) groups quickly, which resulted in the microstructure's difference. Further analysis showed the NaCS-CS-PPS microcapsules and NaCS-WSC-PPS microcapsules had lower swelling ratios due to their tighter interior microstructures that formed. The cross-linking agent had important effect on the total mass of PECs that produced; moreover, the decline of zeta potential of NaCS-CS-PPS microcapsules was lower than that of NaCS-CS microcapsules, similar trend was found in the NaCS-WSC-PPS microcapsules compared with NaCS-WSC microcapsules, indicating the PPS participated in the interactions and played a role in the microcapsules' formation process.
Asunto(s)
Cápsulas/química , Celulosa/análogos & derivados , Quitosano/química , Reactivos de Enlaces Cruzados/farmacología , Portadores de Fármacos/química , Polifosfatos/farmacología , Compuestos de Sodio/química , Celulosa/química , Agua/químicaRESUMEN
Environmentally friendly hypervalent iodine reagents are unusually effective promoters of asymmetric α-functionalization of carbonyl compounds. By using hypervalent iodine reagents, various substituents can be introduced into the α-position of carbonyl compounds. In the present review, we briefly survey the asymmetric α-functionalization of carbonyl compound reactions catalyzed by these hypervalent iodine reagents.
Asunto(s)
Electrones , Yodo/química , Compuestos Orgánicos/química , CatálisisRESUMEN
The stable and structurally well-defined Ar-Cu(III) intermediates, that are prepared almost quantitatively from the reaction of azacalix[1]arene[3]pyridines with Cu(ClO(4))(2)·6H(2)O under aerobic conditions, reacted smoothly with a number of alkyllithium reagents under mild conditions to form C(aryl)-C(alkyl) bonds.
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Carbono/química , Cobre/química , Hidrocarburos Aromáticos/química , Litio/química , Compuestos Organometálicos/química , Percloratos/química , Catálisis , Indicadores y Reactivos/química , Modelos Moleculares , Conformación Molecular , Oxidación-ReducciónRESUMEN
Regiospecific halogenation of azacalix[1]arene[3]pyridines at the lower rim position of the benzene ring was achieved from their cross-coupling reaction with cost-effective alkali metal halides through the Cu(ClO(4))(2)-mediated aerobic aryl C-H activation, which gave structurally well-defined aryl-Cu(III) intermediates, and a subsequent C-X bond formation reaction under very mild conditions.
Asunto(s)
Calixarenos/química , Cobre/química , Halógenos/química , Metales Alcalinos/química , Compuestos Organometálicos/química , Piridinas/química , Cristalografía por Rayos X , Halogenación , Enlace de Hidrógeno , Estructura MolecularRESUMEN
Both copper(II)-mediated oxidative C-H bond activation and oxidative addition of copper(I) into a C-I bond produced an identical and structurally well-defined aryl-Cu(III) intermediate. The cross-coupling reaction of an aryl-Cu(III) intermediate with both terminal alkynes at an elevated temperature and alkynyllithium reagents under mild conditions led effectively to the formation of a C(aryl)-C(alkynyl) bond. An alternative mechanism has been proposed for the Castro-Stephens reaction.
Asunto(s)
Alquinos/química , Cobre/química , Hidrocarburos Yodados/química , Compuestos Organometálicos/síntesis química , Piridinas/química , Catálisis , Estructura Molecular , Compuestos Organometálicos/química , Oxidación-ReducciónRESUMEN
Regiospecific functionalization of tetraazacalix[1]arene[3]pyridines at the lower rim position of the benzene ring was achieved conveniently from their cross-coupling reaction with both aliphatic alcohols including chiral primary and secondary alcohols and phenol derivatives through the Cu(ClO(4))(2)-mediated aerobic aryl C-H activation, which gave structurally well-defined aryl-Cu(III) intermediates and a subsequent C-O bond formation reaction under very mild conditions.