Photoredox Catalytic Phosphite‐Mediated Deoxygenation of α‐Diketones Enables Wolff Rearrangement and Staudinger Synthesis of β‐Lactams

Abstract

A novel visible‐light‐driven catalytic activation of C=O bonds by exploiting the photoredox chemistry of 1,3,2‐dioxaphospholes, readily accessible from α‐diketones and trialkyl phosphites, is reported. This mild and environmentally friendly strategy provides an unprecedented and efficient access to the Wolff rearrangement reaction which traditionally entails α‐diazoketones as precursors. The resulting ketenes could be precisely trapped by alcohols/thiols to give α‐aryl (thio)acetates and by imines to afford the valuable β‐lactams in up to 99 % yields.

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

“…Although discovered decades ago, to the best of our knowledge, the potential of this process has not been explored in ketene-involved cycloaddition to construct spiro-β-lactam skeletons. 17 As part of our group's continuous interest in the synthesis of drug-like frameworks, 18 we herein disclosed the first visible-light-mediated sequential Wolff rearrangement and Staudinger cycloaddition reaction between α-diazoketones and pyrazolone ketimines for the assembly of spiro-pyrazoloneβ-lactam derivatives (Scheme 1D). Unlike the photoactivatedα-diazoketone cases reported previously, 16c visible light plays an essential role both in the preparation of ketene from α-diazoketone and the production of the target spiro-pyrazolone-β-lactam proved by the control experiments.…”