The Mechanism of the Reaction of Quinolines with Organolithium Compounds

Abstract The treatment of lepidine (IV) with phenyllithium in ether afforded 2-phenyl-4-methylquinoline (V) along with small amounts of 2-phenylquinoline (VI) and 2-methyl-4-phenylquinoline (VII). The similar treatment of IV with phenyllithium and then with ethyl chloroformate gave 1-ethoxycarbonyl-4-methyl-4-phenyl-1,4-dihydroquinoline (VIIIa). The alkaline hydrolysis of VIIIa produced a mixture of V, VI, and VII. Similar experiments were carried out on the reactions between IV and n-butyllithium and between quinoline and phenyllithium. On the basis of these results and other observations, a new mechanism involving an addition-rearrangement-elimination was proposed for the reaction of quinolines with organolithium compounds.