Palladium catalyzed cross-coupling reactions of organomercurials

Abstract

The palladium catalyzed cross-coupling reactions of methyl mercury iodide provide a mild, selective and general method for the construction of new C-C bond i.e, for the synthesis of arenes. The reaction proceeds in DMF, in the presence of a nucleophilic catalyst (iodide ion), at room temperature under argon atmosphere. Pd° which is generated in the reaction mixture catalyzes the reaction. The catalytic cycle involved in the reaction consists of a sequence of oxidative addition, transmetallation and reductive elimination steps. The role played by the iodide ion as a nucleophilic catalyst is discussed. It forms an ionic complex (Pd 0 I) - and therefore precipitation of palladium black is prohibited. Secondly the formation of ionic complex (CH 3 HgI 2 ) - helps the heterolytic fission of C-Hg bond in transmetallation step. Thus the selectivity of the reaction towards the expected product is enhanced.