Visible Light-Mediated Quantum Dot Photocatalysis Enables Olefination Reactions at Room Temperature

The ability of quantum dots (QDs) to photocatalyze organicreactionsis gaining attention because of their distinct light harvesting propertiesover traditional precious metal- and small molecule-based catalysts.However, establishing the potency of QD photocatalysts in diverseand useful organic transformations, as well as deciphering the chargetransfer mechanism, is essential to cement their place as an efficientphotocatalyst in synthetic chemistry. Here, we report the use of QDsin efficiently catalyzing a series of olefination reactions undervisible-light irradiation at room temperature (90% yield). Spectroscopicand electrochemical studies reveal intriguing insights on the chargetransfer mechanism involved in QD-photocatalyzed olefination. Interestingly,the dual role of triphenylphosphine Ras a surface passivatingagent and nucleophile Rturned out to be decisive in directingthe charge transfer process from the QD to the reactant. Benzyl triphenylphosphoniumbromide salt was accepting the electrons from the photoexcited QDs,thereby initiating the catalytic olefination reaction. QD-photocatalyzedolefination was demonstrated with formaldehyde as well, resultingin the formation of industrially relevant terminal alkene, namelystyrene. Moreover, the environmentally friendly indium phosphide (InP)QD also photocatalyzed the olefination reaction under mild reactionconditions, which proves the practical suitability of our study. Thiswork presents an attractive and efficient way to introduce doublebonds in organic molecules using QDs and visible light at room temperature.