Highly efficient synthesis of isoquinolines via nickel-catalyzed annulation of 2-iodobenzaldimines with alkynes: evidence for dual pathways of alkyne insertion.

[reaction: see text] A wide range of substituted isoquinolines were synthesized via a highly efficient nickel-catalyzed annulation of the tert-butyl imines of 2-iodobenzaldehydes and various alkynes; examination of the regiochemistry of isoquinolines synthesized indicates that there are two different alkyne insertion pathways for the catalytic reactions.