Synthesis of some new 3،4-dimethyl - 3a،7a -dihydropyrano-[2،3-c]-pyrazol-6-(1H)-one derivatives

In this work 3،4-dimethyl-3a,7a-dihydropyrano-[2،3-c]-pyrazol-6-[1H)- one (1) was prepared from ethyl acetoacetate and hydrazine hydrate, which underwent Mannich reaction by reacting it with paraformaldehyde and various secondary amines to give N-Mannich bases (2-9) of compound (1). Reaction of compound (1) with ethyl a-bromoacetate in the presence of anhydrous K^2CO^3 gave ester (10) which converted into the carbohydrazide (11). The azomethines (12-16) were prepared from the corresponding aryl aldehydes and the carbohydrazide (11). Reactions of compound (11) with CS2/KOH, ethyl acetoacetate and acetyl acetone gave oxadiazole (17), pyrazolone (18) and pyrazole (19) respectively. The synthesized compounds were characterized by some spectral data (IR and UV).