A ruthenium-catalyzed approach to the Friedlander quinoline synthesis

In a modification of the Friedlander reaction, 2-aminobenzyl alcohol is oxidatively cyclized with a variety of ketones to yield substituted quinolines. Of all the ruthenium catalysts that were tested for this reaction, the second-generation Grubbs' catalyst gives the highest quinoline yield, in combination with KOtBu as a base. The presence of a hydrogen acceptor is required to regenerate the catalyst. Also the reaction mechanism is discussed, and the results show that there are possibly two different pathways towards quinolines.