Pyrano[4,3‐ b ]pyran‐2,5‐dione, 1. Einfache Synthese von Pyranopyrano‐chinolintrionen

Pyrano[4,3‐ b ]pyran‐2,5‐diones, 1. – Convenient Synthesis of Pyranopyrano‐quinolinetriones Reaction of malondiamides 1 with malonyl chloride ( 5 ) leads to 2,5‐dioxo‐2 H ,5 H 1‐pyrano[4,3‐ b ]pyrans 7 , which readily react with diazomethane to give the corresponding methyl ethers 8 . Thermically induced cyclisation of 8 affords 7 ,12‐dihydro‐2 H ,5 H 1‐pyrano[2′,3′ :4,5]pyrano [2,3‐ b ]quinoline‐2,5,12‐triones 9 . Acidic hydrolysis of 9 yields 4 H 1‐pyrano[2,3‐ b ]quinoline‐4,5(10 H )1‐diones 10 , while basic hydrolysis of 9 gives 4‐hydroxy‐2(1 H )1‐quinolinones 11 .