Polystyrene stabilized Pd-Au nanoalloy for efficient synthesis of bis(indolyl)methanes from aryl iodides using oxalic acid as CO and H2 source

Abstract

Herein, first example of heterogeneously catalyzed carbonylative synthesis of bis(indolyl)methanes from aryl iodides in one-pot and single-step manner has been reported. The reaction was best catalyzed by polystyrene supported bimetallic Pd-Au (Pd-Au@PS) nanoparticles (NPs) in comparison to various supported monometallic Pd-catalysts. The key feature of this protocol involves the application of oxalic acid as economic, solid, and safe multi-functional reagent which acts as a CO, H2 source as well as acid co-catalyst with PEG-200 as green solvent reaction medium for delivering moderate to excellent yields of the desired products, bis(indolyl)methanes (BIMs). The developed protocol is additive, phosphine ligand-free under air/moisture stable recyclable catalyst bearing easy accessibility/affordability to starting materials.