14H‐Naphtho[1′,2′:5,6] pyrano[2,3‐b]quinoline derivatives

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Abstract
Reaction of (N‐alkyl‐N‐phenyl)ethoxycarbonylacetamides with β‐naphthol in the presence of phosphorus oxychloride afforded 1‐oxo‐3‐(N‐alkyl‐N‐phenyl)amino‐1H‐naphtho[2,1‐b]pyrans. These compounds underwent reaction with N,N‐dimethylformamide‐phosphorus oxychloride at 95° yielding a mixture of 14H‐naphtho[1′,2′:5,6]pyrano[2,3‐b]quinoline derivatives and 1‐oxo‐2‐formyl‐3‐(N‐alkyl‐N‐phenyl)amino‐9‐oxy‐1H‐phenalene. When the same reaction was performed at 140°, only 14‐oxo‐14H‐naphtho[1′,2′:5,6]pyrano[2,3‐b]quinoline was obtained in a very good yield. The structures of such compounds were demonstrated by spectral data and by chemical transformations. On the other hand, the expected formylation in the 2 position was achieved when 1‐oxo‐3‐(N‐alkyl‐N‐benzyl)amino‐1H‐naphtho[2,1‐b]pyrans reacted with N,N‐dimethylformamide‐phosphorus oxychloride.