Light-driven Newman–Kwart rearrangement under ambient conditions with cysteine quantum dots

Abstract

The classical Newman–Kwart rearrangement requires harsh reaction conditions (high temperature), resulting in substrate decomposition/side product formation, limiting the scope to electronically deficient substrates to stabilize the anionic transition state in the thermal processes. Thus, it becomes imperative to develop milder protocols for this reaction. The immense potential of nanomaterials as dynamic heterogeneous catalysts, coupled with the scope of photo-mediated transformations, provides a unique opportunity to tackle this challenge. In continuation of our efforts to develop the field of nanomaterial-mediated photocatalysis, we fabricated carbon dots as nanocatalysts to mediate the reaction under ambient temperature and a very short reaction time. Our method was more compatible with electron-rich substrates, corroborating the operation of a cationic mechanism. Interestingly, electronically neutral (and to some extent, electronically poor) substrates were also facile participants in the reaction, showing the robustness and uniqueness of the system in contrast to existing methods. The material could retain its activity for up to ten runs and was compliant with the various parameters associated with a green protocol. This study exemplifies the potential of nanomaterials in mediating otherwise critical synthetic strategies.