Dedicated to the memory of Prof. Dieter Enders
Abstract
Pyrazolone [2,4-dihydro-3H-pyrazol-4-one] represents one of the most important five-membered nitrogen heterocycles
which is present in numerous pharmaceutical drugs and molecules with biological activity.
Recently, many catalytic methodologies for the asymmetric synthesis of chiral pyrazolones
have been established with great success, specially, for the synthesis of pyrazolones
bearing a tetrasubstituted stereocenter at C-4. This review summarizes these excellent
research studies since 2018, including representative examples and some mechanistic
pathways explaining the observed stereochemistry.
1 Introduction
2 Catalytic Enantioselective Synthesis of Chiral Pyrazolones with a Full Carbon Tetrasubstituted
Stereocenter at C-4
3 Catalytic Enantioselective Synthesis of Chiral Pyrazolones with a Quaternary Carbon
Stereocenter at C-4 bearing a Heteroatom
4 Catalytic Enantioselective Synthesis of Chiral Spiropyrazolones
5 Conclusion
Key words
asymmetric catalysis - pyrazolones - organocatalysis - tetrasubstituted stereogenic
centers - nitrogen heterocycles - 2,4-dihydro-3
H-pyrazol-3-ones