STUDIES ON THE COMPETITIVE NICKEL-PROMOTED CARBONYLATIVE INTRAMOLECULAR CYCLIZATION OF VINYL AND ARYL HALIDES WITH HYDROXYALKENES

Ni(CO)4 promotes carbonylative intramolecular cyclization of bromoviny l or iodoaryl substrates bearing suitable hydroxyalkene substituents. In O-protected substrates, alkene insertion takes place exclusively wh ereas lactonization is observed in substrates having a free hydroxyl g roup. Reaction products different from those arising under similar Pd- catalyzed conditions for carbonylations of hydroxyalkenes are observed in the present case. Alternative reaction pathways are proposed to ac count for the products obtained, and the selectivity of these processe s is deduced from the nature of the resulting organic compounds.