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Aldehydes as Photoremovable Directing Groups: Synthesis of Pyrazoles by a Photocatalyzed [3+2] Cycloaddition/Norrish Type Fragmentation Sequence

Ana Pascual-Escudero, Laura Ortiz-Rojano, Silvia Simón-Fuente, Javier Adrio* and María Ribagorda*

*Departamento de Química Orgánica, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain, Email:,

A. Pascual-Escudero, L. Ortiz-Rojano, S. Simón-Fuente, J. Adrio, M. Ribagorda, Org. Lett., 2021, 23, 4903-4908.

DOI: 10.1021/acs.orglett.1c01665

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A photoclick cycloaddition followed by a photocatalyzed oxidative deformylation reaction enable a straightforward regioselective synthesis of pyrazoles. This protocol includes an unprecedented photoredox-catalyzed Norrish type fragmentation under green-light irradiation and offers the use of α,β-unsaturated aldehydes as synthetic equivalents of alkynes.

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proposed mechanism

Key Words

pyrazoles, photochemistry

ID: J54-Y2021