2,3-Substituted quinolines were readily prepared from diallylanilines in good yields under mild conditions by using Co-2(CO)(8) as catalyst.(1,2) Regioselectivity has been explored by examining a series of electron-donating and electron-withdrawing functional groups at ortho, meta, and para positions of the diallylanilines. The results show that both steric and electronic effects influence the isolated yields. Electron-withdrawing groups inhibit the reaction. Solvent effects, temperature effects, and catalyst loadings have also been investigated. Isotopic labeling experiments were devised to permit delineation of the mechanism of reaction.