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 CoI–olefin 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. The cobalt‐catalyzed [2+2+2] cycloaddition of chiral diynes with different nitriles under very mild conditions led to the formation of pairs of diastereomeric biaryl atropisomers in one step. These diastereomers can easily be separated by column chromatography to provide the pure single atropisomers. The 2‐position of the naphthyl ring can further be functionalized.