Utilization of DMSO as a solvent-cum-reactant: synthesis of fused 2-aryl-4-methylquinolines

Herein, we disclose the synthesis of a variety of disubstituted fused quinoline, such as 4-methyl-2-arylbenzo[ h ]quinolines ( 3a-j ), 1-methyl-3-arylbenzo[ f ]quinolines ( 3k-r ), 1-methyl-3-arylnaphtho[2,3- f ]quinolines ( 3s-x ), and 2-aryl-5,7-dimethoxy-4-methylquinolines ( 4a-c ), derivatives from the reaction of an aryl aldehyde with 1-naphthylamine ( 1a ), 2-naphthylamine ( 1b ), 2-aminoanthracene ( 1c ) and 3,5-dimethoxyaniline ( 1d ), respectively, at 80 °C in the presence of 30 mol% (±)-10-camphorsulfonic acid ((±)-CSA) using DMSO as the solvent-cum-reactant. DMSO molecules regioselectively incorporate three carbon atoms into the target molecule in this distinct reaction. The other advantages of the present protocol are that it can be performed under mild reaction conditions and does not require metal catalysts, additional additives or oxidants. Synthesis of a variety of 2,4-disubstituted fused quinolines is reported from the reaction of an aryl aldehyde with a fused aryl amine using DMSO as the source of three carbons.