A Visible-Light-Responsive Octahedral Cage for Efficient and Selective Cross-[2 + 2] Cycloadditions
Rikuya Tanaka, Hiroki Takezawa, Makoto Fujita
Abstract
Host–guest complexation enhances or even alters photoreaction selectivity by preorganizing substrates within the host’s confined cavities. Since most previous hosts exhibited no visible-light absorption, at least one of the reactants needed to be an aromatic compound with UV-light absorption. Here, we developed a visible-light-responsive M 6 L 4 octahedral cage that retains the encapsulation ability of standard M 6 L 4 cages by simply replacing the photoinert metal unit at every vertex with a photoactive cyclometalated Pt(II) unit. This design enabled efficient visible-light-induced cross-[2 + 2] cycloadditions of inert substrates, demonstrating perfect stereo- and site-selectivity via confinement. The selective cross-[2 + 2] cycloaddition was achieved even catalytically, which was impossible with previous M 6 L 4 cages.