An Efficient Synthesis of Unsymmetrical Triarylmethanes -Sequential Incorporation of Aryl Rings by Palladium Catalysts-

Nambo and Crudden have reported an efficient synthesis of unsymmetrical triarylmethanes starting from methyl phenyl sulfone as a readily available template. The three aryl groups are installed through three sequential catalytic arylations. Initial two stepwise C-H arylations of haloarenes catalytically proceed by using Pd(OAc)₂ and [PdCl(allyl)]₂ respectively. A following characteristic arylative desulfonation of aryl boronic acids successfully proceeded by using [PdCl(allyl)]₂ catalyst and N-heterocyclic carbene SIPr ligand. They demonstrate the synthesis of an anti-breast-cancer agent (4-benzyloxyphenyl)(4-methoxyphenyl)(9-phenanthryl)methane using this method.