Visible-light-mediated sequential Wolff rearrangement and Staudinger cycloaddition enabling the assembly of spiro-pyrazolone-β-lactams

Abstract

Visible-light-mediated sequential Wolff rearrangement and Staudinger cycloaddition for the assembly of valuable spiro-pyrazolone-β-lactams for the first time is disclosed by utilizing in situ generated ketenes and pyrazolone ketimines. This powerful approach features high yield, good substrate tolerance, and gram-scale capacity, and provides straightforward access to multisubstituted pyrazole-morpholine skeletons. The control experiments indicate that visible-light-mediated irradiation plays an essential role in the cyclization process, and a plausible mechanism is proposed to explain the observed efficiency.