Diastereomeric Atropisomers from a Chiral Diyne by Cobalt(I)-Catalyzed Cyclotrimerization

The reaction of new, chiral, proline-based naphthyl diynes with different nitriles through a key [2+2+2] cycloaddition reaction step catalyzed by CoIolefin complexes under thermal and photochemical conditions gave diastereomeric atropisomers in good yield and nearly 1:1 ratios. Facile chromatographic separation of the naphthyl tetrahydroisoquinolines gave access to both pure and stable diastereomeric atropisomers. The deprotection and direct functionalization of the methyl- or methoxymethyl-protected 2-naphthyl position of the atropisomers were investigated. The configuration of the formed atropisomers was assigned from results of X-ray studies and circular dichroism spectroscopy.