Acid-catalyzed allenylation of pyrazolones with propargyl alcohols

A TsOH-catalyzed allenylation of pyrazolones with propargylic alcohols has been developed. The established reaction system is well tolerated by a wide scope of pyrazolones and propargylic alcohols. The process has the salient features of operational simplicity, facile scale-up and high yield. In particular, the integration of the pharmaceutical-related pyrazolone skeleton and the allenyl group into a single molecule not only enriches the structural diversity of the pyrazolone scaffold, but potentially also contributes to a broader spectrum of biological activity. Furthermore, it is easy to synthesize 3aa in gram-scale with the yield and efficiency basically maintained, making the practical application of this process more prominent.

Automated summary

The TsOH-catalyzed allenylation of pyrazolones with propargylic alcohols has been developed, showing good tolerance towards a wide range of substrates and offering ease of operation, scalability, and high yield. The integration of pharmaceutical-related pyrazolone skeleton and the allenyl group into a single molecule not only enriches structural diversity but also potentially broadens biological activity. The synthesis of compound 3aa in gram-scale with maintained yield and efficiency highlights the practical application potential of this process.