Stereoinformation Relay: Coupling Diastereoselectivity of a Thermal Diels‐Alder Reaction with the Photochemical Ring‐Closure of Diarylethenes

Abstract

Controlling the stereochemistry, ideally in a reversible manner using external stimuli, is of great importance and appeal for biomedical and materials applications. By incorporating a Diels‐Alder adduct into one of the heteroaromatic rings of a diarylethene, we were able to transfer the exo selectivity of the thermal Diels‐Alder reaction upon photocyclization, leading to the preferred formation of one ring‐closed exo diastereomer in a diastereomeric ratio of 90 : 10. The structures of both ring‐closed exo isomers were assigned based on 2D NMR spectroscopy and DFT calculations. As indicated by both experimental and computational results, the conformational equilibrium of the Diels‐Alder adducts was kinetically trapped in the ring‐closed diarylethenes, leading to successful transfer of stereoinformation. The combination of thermal cycloaddition and photochemical cyclization steps and their associated diastereoselectivity provides ample opportunities to remotely control the transfer of stereoinformation and materials properties with light.