Synthesis of a Nine-Membered Ring via the Intramolecular Ni(II)/Cr(II)-Mediated Coupling Reaction. Unusual Effect of Concentration on the Course of the Reaction

Abstract

The first synthesis of a nine-membered ring by means of an intramolecular Ni(II)/Cr(II)-mediated coupling reaction between an iodoacetylene and an aldehyde is reported. The yield of the reaction is strongly dependent on the substrate concentration, but is independent of both the NiCl₂ and CrCl₂ concentration at high dilution. The application of this methodology to the synthesis of neocarzinostatin chromophore and other natural products is discussed.