Process for preparing pyridazin-3-on derivatives

摘要

A pyridazin-3-on derivative of the formula (1):in which R2 is a hydrogen atom or a C1-C3 alkyl group, R3 is a hydrogen atom or a C1-C3 alkyl group, and Q is an optionally substituted phenyl group can be prepared at a high yield and high purity by ring closing a carboxylic acid derivative of the formula (2):in which R2, R3 and Q are the same as defined above, or its salt in the presence of a nitrogen-containing aromatic compound and a boron compound.