Ugi post-condensation copper-triggered oxidative cascade towards pyrazoles

Abstract

Pyrazolidinones were prepared in a two-step sequence starting from α-hydrazonocarboxylic acids. After a four-component Ugi coupling, the resulting hydrazone was engaged in a copper triggered [3 + 2] cycloaddition/aerobic oxidation cascade.

Keywords

• aerobic oxidation
• copper(II)
• [3 + 2] cycloaddition
• hydrazone
• isocyanide
• pyrazolidinone