By comparison, the classical cyclocondensation of alkylhydrazines with &keto esters gives the regioisomeric pyrazold-ones 2. The reaction solvent employed in these cyclocondensations can have a profound effect on regioisomeric product ratios. Addition of methylhydrazine to 5g in methylene chloride gave regiospecific formation of pyrwlinone 20, whereas addition in watepmethanol mixtures afforded hydroxypyrwle lo as the major ...
