'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 occuring at the surface of Ag NP (C) 2009 Elsevier B.V. All rights reserved.