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 σ-alkylpalladium iodide complexes were isolated and
characterizated.