RESUMEN
The broad application of 1H-indazoles has prompted the development of several approaches for the synthesis of such compounds, including metal-free, palladium-, or copper-promoted intramolecular N-arylation of in situ-generated or isolated o-haloarylhydrazones. Such methods mainly start from o-bromo derivatives due to the better yield observed when compared to those obtained from o-chloroarylhydrazones. However, the o-chloroarylaldehydes and o-chloroarylketones used to prepare the arylhydrazones are more commercially available and less expensive than brominated analogs. Seeking to cover a lack in the literature, this work reports a convenient protocol for the synthesis of N-phenyl- and N-thiazolyl-1H-indazoles by copper-catalyzed intramolecular N-arylation of o-chlorinated arylhydrazones. Therefore, a series of seven N-phenyl derivatives and a series of six novel N-thiazolyl derivatives was obtained in 10-70% and 12-35% yield, respectively, after stirring the o-chlorinated arylhydrazones, CuI, KOH, and 1,10-phenantroline for 12-48 hours in DMF at 120 °C. The products were isolated by column chromatography on silica gel. All products were fully characterized by HRMS as well as 1H and 13C NMR spectroscopy. Thus, this approach is valuable for promoting the synthesis of N-phenyl-1H-indazoles in a higher yield than that reported in the literature using copper catalysis and the same substrates. This study also prompted the first reported synthesis of pharmacologically interesting N-thiazolyl derivatives.
RESUMEN
Anthracene and anthracene derivatives have been extensively studied over the years because of their interesting photophysical, photochemical, and biological properties. They are currently the subject of research in several areas, which investigate their use in the biological field and their application in OLEDs, OFETs, polymeric materials, solar cells, and many other organic materials. Their synthesis remains challenging, but some important preparative methods have been reported, especially in the last decade. This review presents an update of the recent strategies that have been employed to prepare anthracene derivatives. It encompasses papers published over the last twelve years (2008-2020) and focuses on direct and indirect methods to construct anthracene and anthraquinone frameworks.
RESUMEN
A 6-azido-2-tosylenolate, obtained from D-glucono-1,5-lactone in six steps, underwent an intramolecular cycloaddition-elimination pathway under mild conditions, yielding a chiral, substituted 5,6-dihydro-4H-pyrrolo[1,2-c]-1,2,3-triazole. The conditions were optimized to give exclusive formation of the triazole. The mechanism appears to involve intramolecular ring closure via a 1,3-dipolar azide-alkene cycloaddition to give a 1,2,3-triazoline, followed by elimination of p-toluenesulfonic acid, leading to aromatization. Triazole products, obtained by chemical modification, are expected to display activity as enzyme inhibitors. Furthermore, partially protected derivatives of the 2-hexenoate were prepared as useful synthetic intermediates.
Asunto(s)
Inhibidores Enzimáticos/síntesis química , Pirroles/síntesis química , Triazoles/síntesis química , Alquenos/química , Azidas/química , Reacción de Cicloadición , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/farmacología , Estructura Molecular , Pirroles/química , Pirroles/farmacología , Triazoles/química , Triazoles/farmacologíaRESUMEN
A Brønsted acid catalyzed intramolecular cyclization of N-Cbz-protected diazoketones, derived from α-amino acids, is described. The reaction proceeds under metal-free conditions and is promoted by ecofriendly silica-supported HClO4 as the catalyst and methanol as the solvent. This transformation enables the short synthesis of various 1,3-oxazinane-2,5-diones under mild reaction conditions and in good yields (up to 90%). The set-up is very simple; by just mixing all reagents together with no work-up necessary before purification, this protocol takes a greener approach.