# 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.

## Key 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.