Easy Access to Isoquinolines and Tetrahydroquinolines from Ketoximes and Alkynes via Rhodium-Catalyzed C-H Bond Activation

Described herein is a convenient and highly regioselective synthesis of substituted isoquinoline derivatives from various aromatic ketoximes and alkynes via a one-pot, rhodium-catalyzed C-H bond activation. In addition, tetrahydroqulnoline derivatives are formed in good yields from 2-arylidene-1-cyclohexanone oximes possessing an exocyclic double bond and from tetrahydroxanthone oximes. A possible mechanism is proposed that involves chelation-assisted C-H activation via oxidativeaddition of Rh(1) to an ortho-C-H bond, insertion of the alkyne, reductive elimination, intramolecular electrocyclization, and aromatization. This mechanism is supported by isolation of the ortho-alkenylation products 7p and 7q. Also described herein is an example of an iridium-catalyzed activation of an sp(3) C-H bond.