title: Rhodium-Catalyzed Atroposelective [2 + 2 + 2] Cycloaddition of Ortho-Substituted Phenyl Diynes with Nitriles: Effect of Ortho Substituents on Regio- and Enantioselectivity.
abstract: Axially chiral 3-(2-halophenyl)pyridines were successfully synthesized in high yields with excellent enantioselectivity by the cationic rhodium(I)/(S)-H8-BINAP complex-catalyzed atroposelective [2 + 2 + 2] cycloaddition of (o-halophenyl)diynes with nitriles. Interestingly, regio- and enantioselectivity highly depend on ortho substituents on the phenyl group of diynes. When the ortho substituents were methoxy and methoxycarbonyl groups, axially chiral 3-arylpyridines were obtained as a major product, while enantioselectivity was lowered significantly. On the other hand, when the ortho substituents were alkyl groups, regioselectivity was switched to give achiral 6-arylpyridines in high yields.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology , Koganei, Tokyo 184-8588, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kashima
authors.forename: Kota
authors.initials: K
authors.lastname: Teraoka
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Uekusa
authors.forename: Yu
authors.initials: Y
authors.lastname: Shibata
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology , Koganei, Tokyo 184-8588, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Tanaka