6-Amino-3-chloropyridazine → Ethyl 7-chloro-4-oxo-4H-pyrimido[1,2-b]pyridazine-3-carboxylate

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Reaction Steps

A mixture of 3-chloro-6-aminopyridazine [J. Druey et al., Helv. Chim. Acta., 37, 121 (1954)] (8.20 g, 63.56 m mol) and ethyl ethoxymethylenemalonate (15.0 g, 69.4 m mol) in diphenyl ether (70 ml) was heated to distil out ethanol produced. After cooling, the mixture was diluted with n-hexane (300 ml) to precipitate the crude title product, which was dissolved in chloroform (200 ml), treated with a small amount of carbon and evaporated under reduced pressure to 50 ml. The residual solution was diluted with n-hexane (200 ml) to precipitate pure title product. Yield, 7.73 g (56%), M.p. 149°-152° C.

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