Host: Division of Organic Chemistry, The Pharmaceutical Society of Japan
We found very interesting to design a route for the substitution of a phenolic hydroxyl for a halogen. The key step of this transformation is a novel cross-coupling reaction between zinc-silicon reagent and aryl triflates. We have chosen dimethylphenylsilyllithium as a source of silicon due to its ease of preparation from relatively cheap starting materials. An addition of ZnBr2(0.5 equiv.) in THF gave silicon-zinc species. Screening of transition metal catalyst showed that Ni(dppp)Cl2 affords fast and complete conversion of Aryl triflates into corresponding silicon derivate in excellent yield. The aryl dimethylphenylsilanes, obtained via new Ni-catalyzed cross-coupling reaction, can be easily transformed into the corresponding aryl iodides in high yields by treatment with 2 equiv. of iodine monochloride in dichloromethane at 0 °C. Furthermore, the obtained arylsilanes can be converted in good yields into the corresponding boronic esters.