New vistas in quinoline synthesis

The gold-catalyzed Friedlander reaction was applied to the condensation of 2-aminoarylketones with β-keto-esters, β-diketones, β-keto-amides, and β-keto-sulfones to afford a diverse range of 2,3,4-trisubstituted quinolines in 3–82% yield. The seven-membered rings 1,3-cycloheptadione and azepane-2,4-dione reacted smoothly in 75% yield. An alternative procedure for the synthesis of 3-(methanesulfonyl)quinolines was developed and provided an entry into late stage manipulation of the 4-position of these quinolines. The requisite 2-aminoarylketones for the Friedlander reaction were prepared in one pot by modified Sugasawa reaction using gallium(III) chloride and boron(III) chloride in 12–54% yield.