Synthesis of functionalized tetrahydrodibenzo[ b , g ][1,8]naphthyridin-1(2 H )-ones through base-promoted annulation of quinoline-derived dipolarophiles and cyclic enaminones.

An eco-friendly and metal-free method for the synthesis of tetrahydrodibenzo[ b , g ][1,8]naphthyridin-1(2 H )-ones was established. Quinoline-derived dipolarophiles and cyclic enaminones as starting materials undergo a 1,4-Michael addition/S N Ar tandem annulation reaction affording the target products. This approach features transition metal-free conditions, good functional group tolerance and operational simplicity.