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

The Meldrum’s acid-based multi-component reactions have emerged as a highly versatile and valuable tool, offering a 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 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 propose the approach to a reactivity umpolung of arylidene malonates via visible light-driven SET/PT sequence, which enables the radical chemistry in Meldrum’s acid-based MCRs. The viability of the proposed approach is demonstrated by the three-component synthesis of hitherto unknown imidazolinone malonic acids. The radical chain mechanism is evidenced for the disclosed transformation by mechanistic experiments and density functional calculations.