Cross reactions of cyanoacetic acid derivatives with carbonyl compounds 3.* One-step synthesis of substituted 2-amino-5-oxo-4,5-dihydropyrano [3,2-c] chromenes

摘要

Three-component reactions of 4-hydroxycoumarin,carbonyl compounds,and malono-nitrile or alkyl cyanoacetates in ethanol in the presence of Et_3N as a catalyst give substituted 2-amino-5-oxo-4,5-dihydropyrano[3,2-c]chromenes.A key compound in the synthesis(Scheme 1)of warfarin(rodenticide,a blood anticoagulant)is 2-amino-3-cyano-5-oxo-4-phenyl-4,5-dihydropyrano[3,2-c]chro-mene(3)prepared by heating of 4-hydroxycoumarin 1 with benzylidenemalononitrile 2 in pyridine or water.