Simple, straightforward, and atom economic methods for the synthesis of quinolines, 2-aminoquinolines, and quinazolines via biomimetic dehydrogenative condensation/coupling reactions, catalyzed by well-defined inexpensive and easy to prepare singlet diradical Ni(II)-catalysts featuring two antiferromagnetically coupled singlet diradical diamine type ligands are described. Various polysubstituted quinolines, 2-aminoquinolines, and quinazolines were synthesized in moderate to good yields from different low-cost and readily accessible starting materials. Several control experiments were carried out to get insight into the reaction mechanism which shows that the nickel and the coordinated diamine ligands participate in a synergistic way during the dehydrogenation of alcohols.