Regioselectivity in arene-catalyzed reductive lithiation of acetals of chlorobenzaldehydes

The regioselectivity of arene-catalyzed reductive lithiation of acetals of chlorobenzaldehydes strongly depends on the form of lithium metal employed as a reducing agent. According to previous findings, naphthalene catalyzed reductions run in the presence of lithium powder (high Na content) led to competitive metalations of both aromatic carbon–chlorine and benzylic carbon–oxygen bonds. At variance with these results, naphthalene catalyzed reductions run in the presence of lithium wire (either high or low Na content) led to highly regioselective metalation of aromatic carbon–chlorine bonds. These results disclose new possibilities of selective applications of arene-catalyzed reductive lithiation reactions.