Visible-Light-Driven Newman-Kwart Rearrangement (NKR) by Nanomaterials

Abstract

The development of efficient and sustainable methods for energy-intensive organic transformations is crucial for advancing green chemistry. Sunlight could be a potential sustainable energy source for this purpose. Now, achieving chemical transformation with sunlight requires a fundamental understanding of the outcomes of light-matter interaction, particularly the roles of charge carriers and photothermal heat. Nanomaterials such as plasmonic nanoparticles (NPs) and quantum dots (QDs) have emerged as promising alternatives to molecular systems due to their enhanced light-harvesting capabilities and tunable properties. While extensive efforts have been made to improve the yields and selectivity of organic reactions in charge carriers and heat-driven processes independently, their combined influence within a single reaction framework remains largely unexplored. To address this, the current thesis investigates the use of plasmonic AuNPs as a thermoplasmonic heat source and core-only InP QDs as a photocatalyst for promoting the Newman-Kwart rearrangement (NKR): a thermally demanding transformation that converts O-aryl thiocarbamates into S-aryl thiocarbamates. The NKR was chosen both for its synthetic significance in thiol preparation from phenols and for its ability to exhibit distinct mechanistic behavior when driven by either charge carriers or heat. Under optimized conditions, yields of ~54% with InP QDs and ~23% with AuNPs were achieved utilizing charge carriers and photothermal outcomes, respectively. Although these yields are modest compared to conventional methods, this study introduces a unique dual activation strategy that expands the scope of light-driven NKR reactions. Future improvements in catalyst design and reaction conditions may enhance efficiency and selectivity, making this a valuable step toward sustainable organic synthesis.