Regioselective Metalation Reactions of Some Substituted (Methoxymethoxy)arenes

Article abstract of DOI:10.1021/jo00132a022

The methoxymethoxy substituent acts as a relatively strong ortho-directing group in hydrogen-metal exchange reactions.However, the directing effects are influenced by the metalation medium, thus permitting an unusual degree of control of the site of metalation.In conjunction with weak ortho-directing groups, the metalation ortho to the methoxymethoxy group can be directed to either of the ortho positions by controlling the electron-donating capacity of the metalating solvent.In strongly donating solvents the 1,2,4-substitution pattern will arise from a meta-substituted methoxymethoxy arene, while in nondonating solvents the 1,2,3-substitution is favored.In addition, the methoxymethoxy group serves also to enhance the rate of metalation and to stabilize the aryl-metalated products so that some competing addition reactions are supressed.