The regiochemical outcome of a cobalt(II) catalysed C-H activation reaction of aminoquinoline benzamides with unsymmetrical 1,3-diynes under relatively mild reaction conditions can be steered through the choice of diyne. The choice of diyne provides access to either 3- or 4-hydroxyalkyl isoquinolinones, paving the way for the synthesis of more highly elaborate isoquinolines.