We have found visible-light-promoted organophotocatalytic reactions, mediated by pyrenedione (PYD), of aerobic alkylation and aerobic epoxidation of electron-deficient alkenes. Both two isomers, 1,8-PYD and 1,6-PYD, exhibit very high excited state redox potentials (2.12 V and 2.28 V vs SCE), which enable efficient hydrogen abstraction from C-H substrates. Mild and direct C-H bond functionalization of tetrahydrofuran with alkylidenemalononitriles (AMN) have been accomplished with over 90% yield in the presence of 5 mol% of PYD under air, and 18W blue LED light. The substrate scopes can be extended to ethers, thiols, and allylic C-H bond with various electrophilic Michael acceptors. It was proposed that PYD-THF adduct plays a role in the catalytic cycle, and the turnover process was facilitated by the oxygen. Additionally, PYD is an efficient photocatalyst for the epoxidation of electron-deficient alkene with hydrogen peroxide generated in situ by aerobic photooxidation. AMN epoxides could be obtained in 2-propanol under either air or oxygen atmosphere with high yield of 92%. Our works presented the first example of the catalytic use of PYD to promoted the organic transformation, revealing a promising future for PYD as a novel visible light organophotocatalyst.<br/>

Pyrenedione as a metal-free visible-light photocatalyst for aerobic alkylation and epoxidation

2019 Spring National Meeting

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