Process of producing 2-cyano-4-oxo-4H-benzopyran compounds

摘要

There is disclosed a process of producing a 2-cyano-4-oxo-4H-benzopyran compound of the general formula (2): <IMAGE> (2) wherein R1 and R2 are independently hydrogen, halogen, hydroxy, C1-C5 alkyl, C1-C5 alkoxy, nitro or a group of the RCONH wherein R is C1-C20 alkyl, phenyl, phenyl-substituted (C1-C20) alkyl, phenyl (C1-C20)alkoxyphenyl or (C1-C20) alkoxyphenyl. This production process is characterized in that a carboxamide of the general formula (1): <IMAGE> (1) wherein R1 and R2 are each as defined above, is reacted with a dehydrating agent in the presence of a pyridine compound of the general formula (4): <IMAGE> (4) wherein A1 and A2 are independently hydrogen or C1-C5 alkyl. If the final product cannot be obtained as crystals having good filtration properties by ordinary treatments, a novel technique as disclosed herein can provide such crystals by dissolving the reaction product in an organic solvent insoluble or slightly soluble in water; pouring the resultant solution into water; and removing the organic solvent by distillation with stirring to effect the crystallization of the final product.