Simple and efficient one-pot synthesis of N-phenyl-3,5-difunctionalized pyrazoles

A facile one-pot synthesis of N-phenyl-3,5-difunctionalized pyrazoles is described. The dialkyl 2-[(Z)-phenylhydrazono]succinate intermediate, which is prepared in situ from the mixture of phenylhydrazine and dialkyl acetylenedicarboxylate reacts with aroyl chloride or fumaryl chloride to afford the title compounds. Different types of compounds containing COCl functional group were used to investigate the scope and limitation of the reaction. Two -CO2R and -O2C groups at 3- and 5-position are potentially capable to convert to other functional groups. The reaction conditions are relatively mild and the yields are good.