There is disclosed a process of producing a 2-cyano-4-oxo-4H-benzopyran compound of the general formula (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):
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):
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.
本发明公开了一种通式(2)的 2-
氰基-4-
氧代-4H-
苯并
吡喃化合物的生产工艺:
其中 R¹ 和 R² 独立地为
氢、卤素、羟基、C₁-C₅ 烷基、C₁-C₅ 烷
氧基、硝基或 RCONH 的基团,其中 R 为 C₁-C₂₀ 烷基、
苯基、
苯基取代(C₁-C₂₀)烷基、
苯基(C₁-C₂₀)烷
氧基
苯基或(C₁-C₂₀)烷
氧基
苯基。该生产工艺的特征在于通式(1)的羧
酰胺:
其中 R¹ 和 R² 均如上定义,在通式(4)的
吡啶化合物存在下与
脱水剂反应:
其中 A¹ 和 A² 独立地为
氢或 C₁-C₅ 烷基。如果通过普通的处理方法无法获得具有良好过滤性能的结晶体,那么本文公开的一种新技术可以提供这种结晶体,其方法是将反应产物溶解在不溶于
水或微溶于
水的有机溶剂中;将所得溶液倒入
水中;然后在搅拌下通过蒸馏除去有机溶剂,以实现最终产物的结晶。