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Photoinduced single-electron reduction is an efficient method for the mono-selective activation of the C-F bond on a trifluoromethyl group to construct a difluoroalkyl group. We have developed an electron-donor-acceptor (EDA) complex mediated single-electron transfer (EDA-SET) of α,α,α-trifluoromethyl arenes in the presence of lithium salt to give α,α-difluoroalkylarenes. The C-F bond reduction was realized by lithium iodide and triethylamine, two common feedstock reagents. Mechanistic studies revealed the generation of a α,α-difluoromethyl radical by single-electron reduction and defluorination, followed by the radical addition to alkenes. Lithium salt interacted with the fluorine atom to promote the photoinduced reduction mediated by the EDA complex. Computational studies indicated that the lithium-assisted defluorination and the single-electron reduction occurred concertedly. We call this phenomenon fluoride-coupled electron transfer (FCET). FCET is a novel approach to C-F bond activation for the synthesis of organofluorine compounds., (© 2024 Wiley-VCH GmbH.)

The hydrosilylation of alkenes is one of the most important methods for the synthesis of organosilicon compounds. In addition to the platinum-catalyzed hydrosilylation, silyl radical addition reactions are notable as economic reactions. An efficient and widely applicable silyl radical addition reaction was developed by using 2-silylated dihydroquinazolinone derivatives under photocatalytic conditions. Electron-deficient alkenes and styrene derivatives underwent hydrosilylation to give addition products in good to high yields. Mechanistic studies indicated that the photocatalyst functioned not as a photoredox catalyst but as an energy transfer catalyst. DFT calculations clarified that the triplet excited state of 2-silylated dihydroquinazolinone derivatives released a silyl radical through the homolytic cleavage of a carbon-silicon bond, and this was followed by the hydrogen atom transfer pathway, not the redox pathway., (© 2023 Wiley-VCH Verlag GmbH.)

Supramolecular photocatalysis via charge-transfer excitation of a host-guest complex was developed by use of the macrocyclic boronic ester [2+2] BTH-F containing highly electron-deficient difluorobenzothiadiazole moieties. In the presence of a catalytic amount of [2+2] BTH-F , the triplet excited state of anthracene was generated from the charge-transfer excited state of anthracene@[2+2] BTH-F by visible-light irradiation, and cycloaddition of the excited anthracene with several dienes and alkenes proceeded in a [4+2] manner in high yields., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A conceptually new method for the catalytic electrophilic activation of aromatic carbonyl substrates, by utilizing donor-acceptor interactions between an electron-deficient macrocyclic boronic ester host ([2+2] BTH-F ) and an aromatic carbonyl guest substrate, was realized. In the presence of a catalytic amount of [2+2] BTH-F , dramatic acceleration of the nucleophilic addition of a ketene silyl acetal towards either electron-rich aromatic aldehydes or ketones was achieved. Several control experiments confirmed that inclusion of the aromatic substrates within [2+2] BTH-F , through efficient donor-acceptor interactions, is essential for the acceleration of the reaction., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)