Organocatalyzed Birch Reduction Driven by Visible Light
The Birch reduction is a powerful synthetic methodology that uses solvated electrons to convert inert arenes to 1,4-cyclohexadienes—valuable intermediates for building molecular complexity. This reaction historically requires dangerous alkali metals and cryogenic liquid ammonia as the solvent, severely limiting application potential and scalability. Here, we introduce benzo[ghi]perylene imides as new organic photoredox catalysts for Birch reductions performed at ambient temperature and driven by visible light. Using low catalyst loadings (<1 mole percent), benzene and other functionalized arenes can be selectively transformed to 1,4-cyclohexadienes in good yields. Mechanistic studies support that this unprecedented visible light induced reactivity is enabled by the ability of the organic photoredox catalyst to harness the energy from two visible light photons to affect a single, high energy chemical transformation, likely proceeding through a solvated electron.