One-pot synthesis of xanthones using a novel copper-based magnetically recoverable nanocatalyst

The xanthone nucleus constitutes the core of an important family of natural and biologicallyactive compounds that are widespread in higher plants and microorganisms. These secondary metaboliteshave interesting pharmaceutical properties, among them anti-cancer, anti-thrombotic, anti-hypertensive,anti-bacterial, anti-tumoral, opiaceous, cytotoxic, anti-viral and anti-inflammatory activity. Standard syntheses of the xanthone skeleton typically involve multistep procedures, which generally require theintermediacy of a benzophenone or a diaryl ether, plus harsh reaction conditions, and/or strong acids ortoxic metals are often employed.Herein, we established a versatile and straightforward strategy to construct a xanthone skeleton via anintermolecular catalytic coupling of 2-substituted benzaldehydes and a wide range of phenols. For thispurpose, a novel and magnetically recoverable catalyst consisting of copper nanoparticles on nanosizedsilica coated maghemite in the presence of triphenylphospine is presented. The reaction proceedssmoothly without the need to preactivate the aldehyde carbonyl group. It can tolerate various functionalgroups and provides an efficient protocol for the generation of a small library of functionalized xanthones.The easy recyclability of the catalyst, the potential scalability of the process and the simple reactionconditions combined with the low cost of the starting materials, makes this methodology transferable topharmaceutical purposes.