Pyrazoles Versus Pyrazolo[1,5-a]pyrimidines and Pyridones Versus Enamines: Re-actions of 2-Aryl-3-oxopropanenitrile with Nitrogen and Carbonyl Compounds

AIM and Objective: The present work outlines the synthesis of pyrazoles and pyrazolo[1,5- a]pyrimidines from the reaction of 2-aryl-3-oxopropanenitrile with hydrazine monohydrate under different conditions. Reactions of 2-aryl-3-oxopropanenitrile with 2,4-pentanedione or ethyl acetoacetate furnished a mixture of highly functionalized pyridones and enamines through two different mechanistic pathways under various applied conditions. Material and Method: 2-Aryl-3-oxopropanenitriles were prepared according to literature procedures. Other reagents and solvents were purchased and used without further purification. Reactions were carried out either at 0oC, room temperature or under reflux and product was isolated by filtration or concentration of reaction mixture. Results: This article outlines the synthesis of 5-aminopyrazoles and/or pyrazolo[1,5-α]pyrimidines from the reaction of multi-functional 2-aryl-3-oxopropanenitrile with hydrazine monohydrate under various controlled reaction conditions. When 2-aryl-3-oxopropanenitrile reacted with 2,4-pentanedione or ethyl acetoacetate, highly functionalized enamines and pyridines were formed via two different mechanistic pathways. While, novel ethyl 6-amino-5-(4-chlorophenyl)-2-methylnicotinate was obtained from the reaction of (Z)-Ethyl-3-((Z)- 2-(4-chlorophenyl)-2-cyanovinylamino)but-2-enoate with hydrazine monohydrate in ethanol. Conclusion: 2-Aryl-3-oxopropanenitrile proves to be a promising molecule that can be explored further to synthesize new nitrogen compounds which can be used as building blocks in synthetic heterocyclic chemistry.