In water, Friedländer annulation using Lewis acid-surfactant-combined catalyst provides a mild and efficient route for the synthesis of quinolines. Employing a catalytic amount of scandium tris(dodecyl sulfate) [Sc(O 3 SOC 12 H 25 ) 3 ], various polysubstituted and polycyclic quinolines were obtained in exellent yields.Keywords: Friedländer annulation; Lewis acids; quinoline; surfactant Lewis acid catalysis has attracted much attention in organic synthesis.[1] Recently, a new type of catalyst, "Lewis acid-surfactant-combined catalyst (LASC)", has shown high efficiency in various organic transformations. These reactions are promoted in water without organic cosolvents.[2] Proposed by Kobayashi, [3] this kind of catalyst acts both as a Lewis acid to activate the substrate molecules and as a surfactant to form emulsions in water. The high efficiency of LASC in reactions, as well as creation of environmentally benign processes promoted us to explore the possibility of methodological development in the scaffold construction of natural product-like compounds. The availability of a practical route for the generation of small molecules-based natural products is of utmost urgency and importance in biomedical research. As a privileged fragment, quinoline is a ubiquitous subunit in many quinoline-containing natural products with remarkable biological activities.[4] Members of this family have wide applications in medicinal chemistry.[4] Because of their importance as substructures in a broad range of natural and designed products, a significant effort continues to be given over to the development of new quinoline-based structures [5] and new methods for their construction. [6] As part of a continuing effort in our laboratory toward the development of new methods for the expeditious synthesis of biologically relevant heterocyclic compounds, [7] we became interested in the possibility of developing a novel and efficient method to construct the quinoline scaffold. It is well-known that the protocol reported by Friedländer is one of the most simple and straightforward methods for the synthesis of polysubstituted quinolines, although some methods such as Skraup, Doebner von Miller, and Combes reactions [8] are available. Brønsted acids like sulfamic acid, hydrochloric acid, sulfuric acid, p-toluenesulfonic acid and phosphoric acid were widely used as reagents or catalysts.[9] Recently, various Lewis acids have been reported to be effective for the synthesis of quinolines.[10] However, many of these procedures are complicated by harsh reaction conditions, low yields, difficulties in work-up, and the use of stoichiometric and/or relatively expensive reagents. And in some cases, high catalyst loadings had to be employed in order to obtain respectable yields. Since quinoline derivatives are increasingly useful and important in pharmaceuticals and industry, the development of a simple, eco-and environmentally benign protocol is still desirable. Inspired by the recent advances of "Lewis acid-surfactant-combined catalysts ...