Synthesis of highly functionalised spiro-indoles by a halogen atom transfer radical cyclization

The halogen atom transfer radical cyclization (HATRC) has been evaluated on N-(indolylmethyl) trichloroacetamides under Cu(I) Cl catalysis using nitrogen containing ligands. The ring closure leads to the formation of 3,3-spiro-3H-indoles in moderate to good yields by a 5-exo-mechanism. Derivatives with an N- electron withdrawing substituent also lead to a 5-exo-trig and not to a 6-endo-trig cyclization.