Access to Pyrazolo[1,5‑a]pyrimidinone Regioisomers from Acylated Meldrum’s Acids

TL;DR

This paper presents two efficient methods to selectively synthesize specific pyrazolo[1,5-a]pyrimidinone isomers using acylated Meldrum’s acids.

Contribution

The study introduces a reliable and regioselective synthesis route to underreported pyrazolo[1,5-a]pyrimidin-5-ones using acylated Meldrum’s acids.

Findings

Selective access to pyrazolo[1,5-a]pyrimidin-5-ones or -7-ones is achieved by adjusting reaction conditions.

The method provides high-yield syntheses of pyrazolo[1,5-a]pyrimidinones, a subclass with limited prior synthetic methods.

Acylated Meldrum’s acids are shown to be valuable building blocks for regioselective heterocycle synthesis.

Abstract

Two complementary
and efficient methods for the regioselective
synthesis of functionalized pyrazolo­[1,5-a]­pyrimidinones
were developed from 3-aminopyrazoles and acylated Meldrum’s
acids. Fine-tuning the reaction conditions enables selective access
to either pyrazolo­[1,5-a]­pyrimidin-5-ones or -7-ones
in high yields. This protocol offers a reliable route to pyrazolo­[1,5-a]­pyrimidin-5-ones, a subclass with few reported syntheses,
and highlights the value of acylated Meldrum’s acids as building
blocks for regioselective heterocycle synthesis and biologically relevant
scaffold generation.

Figures