N-alkyl Tetronamides as Ambident Nucleophilic building blocks for the Synthesis of new 4-Aza-2,3-didehydropodophyllotoxins

Aza-analogues of podophyllotoxin were synthesized in two steps from N-substituted tetronamides. The acid-mediated benz­hydrylation of N-substituted tetronamides with a suitably functionalized benzhydrol quantitatively afforded the cyclization precursors. The target pentacyclic 4-aza-2,3-didehydropodo-phyllotoxins were next obtained via an intramolecular copper-mediated Ullmann-type N-arylation.