Elaborating E/Z-Geometry of Alkenes via Cage-Confined Arylation Catalysis of Terminal Olefins

A visible light photosensitizing metal-organic cage is applied as an artificial supramolecular reactor to control the reaction of aryl radicals with terminal olefins under green light/solvent conditions, which facilitates selective transformation in the confined enzyme-mimicking environment to give a series of geometrically defined E/Z-alkenes. The hydrophobic cage displays good host-guest inclusion with aromatic substrates, promoting Meerwein arylation and protecting E-isomeric products during reaction; while a small amount of benzonitrile can turn on efficient E→Z isomerization. Besides π-π stacking, the hydrogen bonding and halogen bonding interactions also act as control forces for the arylation of aliphatic terminal olefins known as poor acceptors in classic Meerwein arylation. The application of this switchable cage-confined arylation catalysis has been demonstrated by the syntheses of Tapinarof and a marine natural product from the same substrate via controllable E/Z selectivity.