Herein, we report the development of a new method for the syntheses of substituted triphenylenes from the corresponding 1,2,4-trisubstituted arenes, which were themselves generated in a highly regioselective manner according to an intermolecular alkyne cyclotrimerization reaction that was catalyzed by a novel Co-TMTU complex. This highly regioselective reaction for the formation of 1,2,4-trisubstituted arenes will be a valuable addition to the plethora of tools already available to synthetic chemists and encourage further mechanistic studies of this important alkyne trimerization process.