10.1021/ol006852l
The research describes a novel and efficient method for synthesizing 3-indolyl-2,5-dihydroxybenzoquinones, a substructure found in biologically significant natural products like the asterriquinones, which are known for their antitumor properties and other biological activities. The purpose of the study is to develop a synthetic route that could be used in the total syntheses of asterriquinones or to prepare reagents for probing the biological activity of indolylquinones. The process involves the acid-catalyzed condensation of indoles with 2,5-dichlorobenzoquinone, followed by DDQ oxidation, resulting in dichloroquinones that are then hydrolyzed to produce the 3-indolyldihydroxybenzoquinones.
10.1039/b712227f
The research aims to develop a method for synthesizing indoles with sterically demanding N-substituents using palladium-catalysed tandem aryl and alkenyl C–N bond formation. The study addresses the challenge of synthesizing N-substituted indoles, which are important for their biological and medicinal properties but difficult to produce due to the low nucleophilicity of indole nitrogen atoms. The researchers optimized a catalyst system using Pd(OAc)2, HBF4–PtBu3 ligand, and NaOtBu as base in toluene solvent at 130°C to achieve efficient coupling of bulky amines with dihalogenated styrenes. They demonstrated the versatility of their method by synthesizing a range of indoles with various sterically demanding N-nucleophiles and different styrene substrates. The utility of this method was further highlighted by a short synthesis of the natural product demethylasterriquinone A1, showcasing the potential for creating complex indole-based structures with significant biological functions.