# 4,5-Dihydro-2H-pyridazin-3-ones as a Platform for the Construction of Chiral 4,4-Disubstituted-dihydropyridazin-3-ones

## TL;DR

This paper presents a new method to synthesize chiral dihydropyridazin-3-ones using 4,5-dihydro-2H-pyridazin-3-ones as a starting platform.

## Contribution

A novel asymmetric synthesis pathway for 4,4-disubstituted dihydropyridazin-3-ones using chiral catalysts is introduced.

## Key findings

- Chiral ammonium salt phase-transfer catalysts enable enantioselective conjugate additions to DHPDOs.
- The method allows for the formation of all-carbon stereocenters in dihydropyridazin-3-one derivatives.
- Moderate to good enantioselectivities and reasonable yields are achieved with acrylate and quinone methide substrates.

## Abstract

4,5-Dihydro-2H-pyridazin-3-ones (DHPDOs) are important synthetic as well as naturally occurring heterocycles. We herein report the synthesis of various 4-monofunctionalized 4,5-dihydro-2H-pyridazin-3-ones and their use as starting materials to access 4,4-disubstituted dihydropyridazin-3-ones in an asymmetric fashion. By using chiral ammonium salt phase-transfer catalysts, conjugate additions of these scaffolds to classical acrylate-based Michael acceptors, as well as quinone methides, can be carried out with moderate to good enantioselectivities and in reasonable yields, affording a new pathway to dihydropyridazin-3-one derivatives with an all-carbon stereocenter.