Easy Access to 1-Amino and 1-Carbon Substituted Isoquinolines via Cobalt-Catalyzed C-H/N-O Bond Activation

A green atom-economical method for the synthesis of highly functionalized 1-amino and 1carbon substituted isoquinolines from the reaction of N'-hydroxybenzimidamides and aryl ketoximes, respectively, with alkynes via pentamethylcyclopentadienylcobalt(III)-catalyzed C-H/N-O bond activation is described. The external oxidant-free annulation reaction uses the = NOH moiety in N'-hydroxybenzimidamides or N-aromatic ketone oximes as the directing group and internal oxidant. This first row transition metal-catalyzed annulation serves as an efficient alternative for the synthesis of isoquinolines, as water is the only by-product and expensive noble metals such as rhodium(III), iridium (III), palladium (II), and ruthenium(II) are not required. The reaction proceeds via C-H activation, alkyne insertion, reductive elimination, and N-O activation.