Some Reactions with Indane‐1,3‐dione: A Facile Synthesis of Pentacycline Heterocyclic Analogues

Indane‐1,3‐dione 1 reacts with salicylaldehyde 5 and malononitrile 3 to afford 6‐amino‐7‐imino‐7 H ‐indeno‐[2′,1′:5,6]‐pyrano‐[3,4 ‐ c ]‐chromene 6 , which could be transformed into the corresponding 7‐oxo derivative 7 . 2‐(3‐Oxoindan‐1‐ylidene)‐malononitrile 10 couples with the diazonium salts 8 , 14 , and 15 to afford after cyclization the indeno‐[2,1‐ c ]‐pyridazine 13 and the indeno‐[2′,1′:3,4]‐pyridazino‐[1,6‐ a ]‐quinazoline derivatives 20 and 21 , respectively.