An umpolung of transient arylidene malonates via photoactivated one-electron reduction: the application to the catalyst-free multicomponent synthesis of imidazolinone malonic acids

Abstract

Meldrum's acid-based multi-component reactions have emerged as a highly versatile and valuable tool, offering simple access to numerous classes of pharmaceutically and industrially valuable heterocyclic and acyclic organic compounds. The vast majority of these reactions employ a carbonyl compound as one of the reagents and utilize the electrophilic reactivity of transient arylidene malonates. This necessarily requires a third nucleophilic reagent and represents the general limitation of these reactions. Herein, we proposed an approach to a reactivity umpolung of arylidene malonates via a visible light-driven SET/PT sequence, enabling the radical chemistry in Meldrum's acid-based MCRs. The viability of the proposed approach was demonstrated by the three-component synthesis of hitherto unknown imidazolinone malonic acids. The radical chain mechanism was evidenced for the disclosed transformation by mechanistic experiments and density functional calculations.