Recent Advances in Catalytic Enantioselective Synthesis of Pyrazolones with a Tetrasubstituted Stereogenic Center at the 4-Position

Abstract Pyrazolone [2,4-dihydro-3 H -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