‘Green’ chitosan bound silver nanoparticles for selective C–C bond formation via in situ iodination of phenols

Herein we report on the use of chitosan–Ag NP composite as an efficient catalyst in selective C–C coupling of phenolic compounds in the presence of molecular iodine. This is the first report on the C–C coupling with Ag NPs as the catalyst. The reactions were carried out with phenol and a few of its derivatives as well as naphthols. The results indicate that the reaction proceeded via the formation of p-iodophenol followed by o–p coupling leading to the products. The reactions were complete in 3 h with high yields. When the para-position of phenol was blocked by a substituent then iodination at the ortho-position could only be observed and the formation of coupled products did not occur. In the case of naphthols o–o coupling could only be observed. Based on the results a mechanism is proposed for the coupling reaction occurring at the surface of Ag NP.

Graphical abstractAg nanoparticles (NPs) embedded in a composite with ‘green’ chitosan could catalyze C–C coupling reaction of phenols (ortho–para) in the presence of iodine, in a short time and at room temperature, with high selectivity and yield.Figure optionsDownload full-size imageDownload as PowerPoint slide