Synthesen von Heterocyclen, 32. Mitt.: Über kondensierte N-Heterocyclen

6‐Methoxy‐2‐oxo‐1,2‐dihydroquinoline‐3,4‐dicarbonitriles, A Red Compound Class with Solvent and pH Independent Green Fluorescence Maxima

“…Our approach started from p ‐anisidine ( 1 ) and malonic acid ( 2 ) using phosphoryl chloride as cyclization agent similar as described in Refs. . Phosphoryl chloride is reported to act in two steps, first to convert malonic acid ( 2 ) to a reactive malonic‐halfamide intermediate, and then as cyclocondensation agent for the acylation at the reactive aromatic amine 1 .…”

“…Phosphoryl chloride is reported to act in two steps, first to convert malonic acid ( 2 ) to a reactive malonic‐halfamide intermediate, and then as cyclocondensation agent for the acylation at the reactive aromatic amine 1 . In the literature , quinolone 4 was obtained in 63% yield; and as by‐product, N , N ′‐bis(4‐methoxyphenyl)malonamide ( 3 ) was obtained in 32% yield. Optimization attempts by changing the ratio of p ‐anisidine, malonic acid, and phosphoryl chloride, reaction time and work‐up gave best results when only a small excess of phosphoryl chloride and a reaction temperature of 90–95 °C for 90 min were used, then pouring the mixture onto ice water and doing work‐up by dissolving the crude material in a large excess of 1 M sodium hydroxide solution.…”

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“…The starting material 2-amino-1H-imidazol [4,5-b]pyridine (12) was prepared in excellent yield by treating 2,3-diaminopyridine with cyanamide according to the method of Weiss et al [21]. As illustrated in the reaction Scheme 3, 12 might be produced in isomeric form.…”