New 4-spiroannulated tetrahydroisoquinolines by a one-pot sequential procedure.: Isolation and characterization of σ-alkylpalladium Heck intermediates

A simple and efficient entry to new tetrahydroisoquinolines 4-spiroannulated to a five-membered heterocyclic ring has been achieved starting from secondary N-allylamines and involving sequential 2-iodobenzylation/intramolecular Heck reaction/1,3-dipolar cycloaddition. A variety of Heck cyclization conditions were surveyed. When using Pd(PPh3)(4) as catalyst, stable sigma-alkylpalladium iodide complexes were isolated and characterizated.