Fluorinated fused rings are challenging to construct from simple starting materials. Herein, we report the first photocatalyzed cascade reactions of readily available cyclopropanols and α-trifluoromethylsubstituted olefins for the synthesis of fused gemdifluorooxetanes. Two rings and three bonds were efficiently constructed in one reaction. The reaction showed broad substrate scope and the downstream transformations of the products demonstrated the synthetic potential of the reaction. The mechanistic study supported the presence of cascade photoredox catalysis and energy transfer catalysis/direct photoexcitation processes.

Controlling the reactivity of reactive intermediates is essential to achieve selective transformations. Due to the facile 1,5-hydrogen atom transfer (HAT), alkoxyl radicals have been proven to be important synthetic intermediates for the δ-functionalization of alcohols. Herein, we disclose a strategy to inhibit 1,5-HAT by introducing a silyl group into the α-position of alkoxyl radicals. The efficient radical 1,2-silyl transfer (SiT) allows us to make various α-functionalized products from alcohol substrates. Compared with the direct generation of α-carbon radicals from oxidation of α-C-H bond of alcohols, the 1,2-SiT strategy distinguishes itself by the generation of alkoxyl radicals, the tolerance of many functional groups, such as intramolecular hydroxyl groups and C-H bonds next to oxygen atoms, and the use of silyl alcohols as limiting reagents.

Fluorinated fused rings are challenging to construct from simple starting materials. Herein, we report the first photocatalyzed cascade reactions of readily available cyclopropanols and α-trifluoromethylsubstituted olefins for the synthesis of fused gemdifluorooxetanes. Two rings and three bonds were efficiently constructed in one reaction. The reaction showed broad substrate scope and the downstream transformations of the products demonstrated the synthetic potential of the reaction. The mechanistic study supported the presence of cascade photoredox catalysis and energy transfer catalysis/direct photoexcitation processes.

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