With Cyanogen and Its Derivatives

In 1869, cyanogen and anthranilic acid, when set aside in ethanol for a week, produced a mysterious substance,317 which was later identified as 2-ethoxyquinazolin-4-one (172).318 Somewhat similarly, 6-aminoindazole-5-carboxylic acid, when stirred with cyanogen in methanol for 5 hr at 0°C, was converted, in good yield, to 7-methoxypyrazolo[4,3-g]quinazolin-5-one (173).319 In each case, the amino group in the starting material apparently became converted to an —NHC(NH)CN group. 

Cyanogen bromide and sodium 2-aminobenzoate readily give 2-cyan-aminobenzoic add, which cyclizes spontaneously to 2-aminobenz[3,l] oxazin-4-one (174) (quantitative overall yield), which is converted by methyl-amine to 3-methylquinazoline-2,4-dione in two stages but in excellent yield. Arylamines behave similarly.316 

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