Synthesis of Tetrahydro‐4H‐pyrido[1,2‐b]isoquinolin‐4‐ones from Ugi 4‐CR‐Derived Dihydroisoquinoline‐Xanthates

An efficient protocol for the synthesis of poly‐functionalized 1,2,3,6‐tetrahydro‐4H‐pyrido[1,2‐b]isoquinolin‐4‐ones is described. First, propargyl‐containing Ugi adducts were transformed to polysubstituted dihydroisoquinolines by an intramolecular Au‐catalyzed alkyne hydro‐arylation, followed by the alkene isomerization process. Then, these pivotal intermediates were engaged in a xanthate‐based oxidative radical cascade addition/cyclization process with a suitable alkene. In this work, an efficient protocol for the synthesis of densely functionalized 1,2,3,6‐tetrahydro‐4H‐pyrido[1,2‐b]isoquinolin‐4‐ones from propargyl‐containing Ugi adducts is reported.