Efficient Synthesis of Tetrahydro-β-carbolin-1-one and Dihydroisoquinolin-1-one Derivatives as Versatile Intermediates

An efficient one-pot procedure is described in which an isocyanate intermediate, generated from the corresponding carboxylic acid by a modified Curtius rearrangement, is captured by a tethered aromatic ring in the presence of BF3 center dot OEt2 to generate various lactams, including tetrahydro-beta-carbolin-1-one and dihydroisoquinolin-1-one derivatives.