RESUMEN
The use of state-of-the-art separation tools from the pharmaceutical industry for addressing intractable separation problems from academic synthetic chemistry is evaluated, showing fast and useful results for the resolution of complex mixtures, separation of closely related components, visualization of difficult to detect compounds and purification of synthetic intermediates. Some recommendations for potential near term deployment of separation tools within academia and the evolution of next generation separation technologies are discussed.
Asunto(s)
Fraccionamiento Químico/métodos , Industria Farmacéutica/métodos , Compuestos Orgánicos/síntesis química , Compuestos Orgánicos/aislamiento & purificación , Técnicas de Química Sintética , Cromatografía Líquida de Alta Presión , Cromatografía con Fluido Supercrítico , Laboratorios , Compuestos Orgánicos/químicaRESUMEN
A practical, palladium-catalyzed synthesis of aryl fluorides from arylboronic acid derivatives is presented. The reaction is operationally simple and amenable to multigram-scale synthesis. Evaluation of the reaction mechanism suggests a single-electron-transfer pathway, involving a Pd(III) intermediate that has been isolated and characterized.
Asunto(s)
Derivados del Benceno/síntesis química , Ácidos Borónicos/síntesis química , Flúor/química , Paladio , Catálisis , HalogenaciónRESUMEN
Pnictogen complexes are ideal for mediating multi-electron chemical reactions in two-electron steps. We report an Sb(v) bis-µ-oxo corrole that photochemically oxidises the C-H bonds of organic substrates. In the case of toluene, the substrate is oxidised to benzaldehyde, a rare example of a four-electron photoreaction.
Asunto(s)
Antimonio/química , Porfirinas/química , Benzaldehídos/química , Electrones , Modelos Moleculares , Estructura Molecular , Oxidación-Reducción , Procesos FotoquímicosRESUMEN
A Brønsted base activation mode for oxidative, Pd(II)/sulfoxide-catalyzed, intermolecular C-H allylic amination is reported. N,N-diisopropylethylamine was found to promote amination of unactivated terminal olefins, forming the corresponding linear allylic amine products with high levels of stereo-, regio-, and chemoselectivity. The predictable and high selectivity of this C-H oxidation method enables late-stage incorporation of nitrogen into advanced synthetic intermediates and natural products.
Asunto(s)
Carbono/química , Hidrógeno/química , Aminación , Productos Biológicos/química , Carbamatos/química , Catálisis , Concentración de Iones de Hidrógeno , Oxidación-Reducción , Paladio/químicaRESUMEN
Efficient C-H functionalization requires selectivity for specific C-H bonds. Progress has been made for directed aromatic substitution reactions to achieve ortho and meta selectivity, but a general strategy for para-selective C-H functionalization has remained elusive. Herein we introduce a previously unappreciated concept that enables nearly complete para selectivity. We propose that radicals with high electron affinity elicit arene-to-radical charge transfer in the transition state of radical addition, which is the factor primarily responsible for high positional selectivity. We demonstrate with a simple theoretical tool that the selectivity is predictable and show the utility of the concept through a direct synthesis of aryl piperazines. Our results contradict the notion, widely held by organic chemists, that radical aromatic substitution reactions are inherently unselective. The concept of radical substitution directed by charge transfer could serve as the basis for the development of new, highly selective C-H functionalization reactions.