Acid/base-co-catalyzed cyclization of ketones with o-amino-benzylamines: Direct synthesis of quinoline compounds

A novel acid/base-co-catalyzed tandem cyclization of various ketones with o-amino-benzylamines employing molecular oxygen as the clean oxidant has been described. The reaction provides an efficient and general strategy for the construction of fused N-heterocyclic compounds, such as dihydrobenzo[c]acridines, indeno[1,2-b]quinolines, dihydro-5H-benzo[6,7]cyclohepta[1,2-b]- quinolines and quinolones in a single step. The broad scope and the use of oxygen as the sole oxidant make this transformation an attractive approach for the synthesis of the above mentioned scaffolds.