Unlocking Photocycloaddition Reactivity of Tropolone by Cage-Confined Visible-Light Photocatalysis for Multilevel Selective Transformation.

The precise asymmetric photochemical transformation of organic compounds containing multiple reactive sites presents significant progress in synthetic chemistry. Herein, we report an unprecedented visible-light-induced cascade transformation of tropolone cyclic triene derivatives by using chiral photoactive metal-organic cages (cPMOCs) as enzyme-mimicking multipocket photocatalysts. The cage-confined photocatalysis promotes three successive elementary steps, i.e., enantioselective [2 + 2] photocycloaddition with chalcone, regio-, and diastereoselective α-ketol rearrangement, and a stereoselective 1,3-acyl shift, resulting in bicyclo[3.2.2]nonane skeleton with multichiral-centers unattainable by other methods. This study demonstrates how complex synthetic challenges of peri-, chemo-, and stereoselectivities could be subtly manipulated by cage-confined supramolecular catalysis for exploration of new reactivities.