Intramolecular Cyclization of Vinyldiazoacetates as a Versatile Route to Substituted Pyrazoles

Abstract

Vinyldiazo compounds undergo a thermal electrocyclization to form pyrazoles in yields of up to 95%. The reactions are operationally simple, use readily available starting materials, require no intervention of a catalyst, and enable the synthesis of mono-, di- and tri-substituted pyrazoles. With the ability to produce highly substituted pyrazole and the flexibility in installing various types of substituents, this method constitutes a new entry to this valuable heterocyclic scaffold of interest in all branches of chemical industry.

Vinyldiazo Compounds as 3-Carbon Radical Acceptors: Synthesis of 4-Fluoroacridines via Visible-Light-Promoted Cascade Radical Cyclization

“…However enticing this proposal might appear, it was conceived to have two major challenges: (1) How will initial radical A be generated if less reactive C–Cl was used? (2) If photocatalyst was employed to generate radical A , how will the background pyrazole formation mediated by light or base be suppressed? Here, we report the results of our research.…”