Enantioselective Access to Bicyclo[4.2.0]octanes by a Sequence of [2+2] Photocycloaddition/Reduction/Fragmentation.

Tricks of the trade: Because intramolecular Cu‐catalyzed access to bicyclo[4.2.0]octanes is not feasible, an oxygen bridge was introduced to facilitate the [2+2] photocycloaddition. Starting from compounds similar to 1, products such as 2 could be obtained enantioselectiviely in three steps after ring‐opening metathesis (see scheme). [ABSTRACT FROM AUTHOR]