Mechanistic Insights into the Light-Driven Difunctionalization of Alkenes with a Sulfonyl-Based Reagent: A Catalyst-Free Approach

Visible-light-mediated difunctionalization of nonactivated alkenes offers a sustainable and efficient strategy for constructing diverse molecular frameworks relevant to medicinal chemistry, polymer science, and synthesis of fine chemicals. While established approaches─such as photoredox catalysis, energy transfer (EnT), and ligand-to-metal charge transfer (LMCT)─have demonstrated success, they typically require external photocatalysts to achieve high reactivity. Alternatively, electron donor-acceptor (EDA) complexes have been explored, but these methods often rely on specially designed substrates, limiting the scope of this reaction. To overcome these limitations, we present a DFT-guided approach for identifying suitable radicals for light-mediated difunctionalization of nonactivated alkenes, eliminating the requirement of auxiliary catalysts or reagents. Our DFT calculations elucidate general reaction mechanisms and provide insights into regioselectivity. Additionally, time-dependent DFT (TD-DFT) calculations are employed to simulate UV-vis spectra and analyze the orbitals involved in key photoinduced transitions, guiding the selection of appropriate light sources. We further investigated the electrophilic and nucleophilic properties of the generated radicals to predict the regioselectivity of their additions. This study provides a framework for designing atom-economical difunctionalization reactions without relying on photocatalysts or substrate-specific EDA complexes and opens new avenues for further development in this area.