Convenient Synthesis of Furo[3,2-b]quinolin-4(1H)-ones

In this work, we report the simple synthesis of furo[3,2-b]quinolin-4(1H)-ones from readily available 4-ethynyl-[1,3]dioxolo[4,5-c]quinolone as the key starting material. After Sonogashira (hetero)arylation, formation of the furoquinoline scaffold was accomplished using methanesulfonic acid and metal-free conditions. Although the cyclization was affected by the substitution of reaction intermediates, the method allowed the preparation of derivatives varying at the C3-position.