Co-catalyzed tandem Pauson-Khand type reaction/dimerization of terminal diynes in the presence of cyclopentadiene under CO pressure

Abstract

Transition metal-catalyzed tandem reactions have attracted much attention due to their operational and economical efficiency in the synthesis of complex organic molecules.1,2 In particular, if an intermediate is highly reactive, its further transformation in a single operation will broaden the utility of the highly reactive intermediate molecule in organic synthesis. Synthesis of novel cyclic compounds through cobalt carbonyl-catalyzed tandem cyclization including the Pauson-Khand and the related reaction has been one of our current research themes.3 Recently, we reported the utilization ofthe highly reactive cyclopentadienone,4 which was produced by a Pauson-Khand reaction, for the synthesis of polycyclic compounds in a tandem fashion.3b,3c Herein, we report cobalt-catalyzed intramolecular carbonylative cycloaddition ofterminal diynes and a subsequent intermolecular cobalt-catalyzed [2+2+2] cycloaddition between the cyclopentadienone intermediate and the starting terminal diyne compound in the presence of cyclopentadiene.