An Organocatalytic System for <i>Z</i>‑Alkene Synthesis via a Hydrogen-Bonding-Assisted Photoinduced Electron Donor–Acceptor Complex

A general catalytic donor for the combination of a photoinduced electron donor–acceptor (EDA) complex and energy transfer was developed. This mild and metal-free protocol allows facile access to various <i>Z</i>-alkenes. Mechanism studies revealed that the organophotocatalyst, 4-CzIPN, formed a distinct three-component EDA complex with redox-active esters and (C₆H₅O)₂P(O)OH to trigger the photoredox catalysis. The <i>E</i> → <i>Z</i> isomerization was achieved via electron exchange energy transfer from 4-CzIPN.