Asymmetric synthesis of axially chiral 1-aryl-5,6,7,8-tetrahydroquinolines by cobalt-catalyzed [2 + 2 + 2] cycloaddition reaction of 1-aryl-1,7-octadiynes and nitriles

Abstract

The asymmetric synthesis of a range of axially chiral 2-arylpyridines by a cobalt-catalyzed [2 + 2 + 2] cycloaddition reaction is described. The use of a planar chiral (1-neomenthylindenyl)cobalt(COD) complex under photochemical conditions is the key for reacting the 1-naphthyldiynes with a range of differently functionalized nitriles, giving the enantiomeric atropoisomers with high chemical yields and enantiomeric excesses of up to 94% ee.