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Highly Regioselective Synthesis of 3,5-Substituted Pyrazoles from Bromovinyl Acetals and N-Tosylhydrazones

Anne Westermeyer, Quentin Llopis, Gérard Guillamot, Phannarath Phansavath*, Virginie Ratovelomanana-Vidal*

*Institute of Chemistry for Life and Health Sciences, 11 rue Pierre et Marie Curie, 75005 Paris, France, Email: phannarath.phansavathchimie-paristech.fr, virginie.vidalchimie-paristech.fr

A. Westermeyer, Q. Llopis, G. Guillamot, P. Phansavath, V. Ratovelomanana-Vidal, Synlett, 2020, 31, 1172-1176.

DOI: 10.1055/s-0039-1690885



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Abstract

A regioselective 1,3-dipolar cycloaddition of diazo compounds, generated in situ from N-tosylhydrazones, with unactivated bromovinyl acetals, which serve as alkyne surrogates, provides 3,5-disubstituted pyrazoles in good yields. The reaction tolerates N-tosylhydrazones bearing various substituted benzylidene groups, and a range of 3,5-disubstituted pyrazoles.

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Key Words

pyrazoles, 1,3-dipolar cycloaddition, bromovinyl acetals, tosylhydrazones


ID: J72-Y2020