Application of the ortho-lithiation-cyclization strategy to N-benzyl- and N-phenethylamine derivatives

The ortho-lithiation-cyclization of iodinated N,N-diacylphenethylamines provides a convenient method for the preparation of 2-(2-acetoamidoethyl)acetophenones and 2-(2-benzamidoethyl)benzophenones, which could be easily transformed into dihydroisoquinolines. By contrast, the N-ethylamino, N-acetyl-amino, and N-trimethylsilylamino moieties studied as ortho-directing groups provide poor assistance to the metalation of N-benzyl- and N-phenethylamines and the corresponding isoindolone or isoquinolone derivatives are obtained in low yields.