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

Abstract

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.