A Novel Synthesis of 4-Pyridazineacetic Acids via Ring Expansion of N-Cyanomethylated 3-Pyrazoline-4-acetic Acids

[摘要]：A novel synthetic route to 4-pyridazineacetic acids 1012 has been achieved by the ring-expansion reaction of N-cyanomethylated 3-pyrazoline-4-acetic acids 79. 1H-Pyrazole-4-acetic acids 13 were reacted with iodoacetonitrile in the presence of triethylamine in refluxing acetonitrile to give the corresponding C-cyanomethylated 1H-pyrazole-4-acetic acids 46 as major products together with N-cyanomethylated 3-pyrazoline-4-acetic acids 7 and 8 as minor products. On the other hand, reactions of 1 and 3 with chloroacetonitrile in the presence of triethylamine in refluxing chloroform afforded the corresponding N-cyanomethylated 3-pyrazoline-4-acetic acids 7 and 9 as major products. Thermal treatment of 79 with sodium hydride in N,N-dimethylformamide caused ring expansion to yield the corresponding 4-pyridazineacetic acids 1012.

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