Friedländer reaction of 3‐acetyltropolones: Synthesis of naphthyridinyl‐ and allied heterocyclic‐substituted tropolones

Five 3‐acetyltropolones reacted with 2‐amino‐3‐pyridinecarbaldehyde to afford the corresponding 3‐(1,8‐naphthyridin‐2‐yl)tropolones in excellent yields. In a similar manner, 1,6‐naphthyridin‐2‐yl‐,1,7‐naphthyridin‐2‐yl‐, 6‐pyrido[2,3‐ b ]pyrazinyl‐, and 1‐methyl‐6‐pyrazolo[5,4‐ b ]pyridyl‐substituted tropolones were prepared. Reactivities of amino‐substituted heteroarenecarbaldehydes in these reactions and properties of the products are also discussed.