Synthesis of Pyrazoles Utilizing the Ambiphilic Reactivity of Hydrazones
Haruo Matsuzaki, Norihiko Takeda, Motohiro Yasui, Yuta Ito, Keiji Konishi, Masafumi Ueda
Abstract
A Brønsted acid-mediated synthesis of pyrazoles from conjugated hydrazones through a β-protonation/nucleophilic addition/cyclization/aromatization sequence was developed. This protocol utilizing the ambiphilic reactivity of hydrazones enables not only self-condensation but also cross-condensation, affording multisubstituted pyrazoles in high yields, with a broad substrate scope. This sequential reaction proceeds under mild conditions via a simple operation. Moreover, the method can be applied to the synthesis of a nonsteroidal anti-inflammatory drug, Lonazolac.
Topics & Concepts
ChemistryAromatizationReactivity (psychology)Combinatorial chemistrySubstrate (aquarium)Conjugated systemProtonationNucleophileCondensationOrganic chemistryCatalysisPhysicsMedicineThermodynamicsOceanographyGeologyPathologyPolymerIonAlternative medicineClick Chemistry and ApplicationsSynthesis and Catalytic ReactionsChemical Synthesis and Analysis