Synthesis of triazolo- and tetrazolo-tetrahydroisoquinolines and isoquinolines via temperature controlled palladium catalysed allene/azide incorporation/intramolecular 1,3-dipolar cycloaddition cascades

A novel palladium catalysed three-component process is described involving an allene, an aryl iodide containing an activated alkene and TMSN3. The cascade proceeds via a (π-allyl)palladium species which is intercepted by azide anion followed by stereoselective intramolecular 1,3-dipolar cycloaddition of the organoazide to afford substituted triazolo- and tetrazolo-tetrahydroisoquinolines in good yield. These latter products undergo extrusion of nitrogen to afford isoquinolines at 100 °C.