3,4-Dimethoxy-6-nitrobenzamide → 2-Amino-4,5-dimethoxybenzamide

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The key starting material, 4-chloro-6,7-dimethoxyquinazoline, was prepared according to published procedures (Nomoto, et al., 1990, Chem. Pharm. Bull., 38:1591-1595; Thomas, C. L., 1970, IN:Catalytic Processes and Proven Catalysts, Academic Press, New York, N.Y.) as outlined below in Scheme 1. Specifically, 4,5dimethoxy-2-nitrobenzoic acid (compound 1) was treated with thionyl chloride to form acid chloride, followed by reacting with ammonia to yield 4,5-dimethoxy-2-nitrobenzamide (compound 2). Compound 2 was reduced with sodium borohydride in the presence of catalytic amounts of copper sulphate to give 4,5-dimethoxy-2-aminobenzamide (compound 3), which was directly refluxed with formic acid to yield 6,7-dimethoxyquinazoline-4(3H)-one (compound 4). Compound 4 was refluxed with phosphorus oxytrichloride to give 4-chloro-6,7-dimethoxyquinazoline (compound 5) in good yield.

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