Decatungstate Anion for Photocatalyzed “Window Ledge” Reactions

• DOI: 10.1021/acs.accounts.6b00339
• Publication Date: 2016-09-20T19:28:29Z
• Authors: Davide Ravelli; Stefano Protti; Maurizio Fagnoni
• Keywords: Visible spectrum

The majority of organic reactions are commonly carried out inside a lab, under fume hood. A particular case is that photochemical reactions, field where the pioneering experiments by Giacomo Ciamician demonstrated more than one century ago different processes can be outdoors, for example, on balcony his own department, upon exposure reacting mixtures to sunlight. main problem related this chemistry "window ledge" most compounds colorless and their absorption in solar light region cases negligible. Recently, impressive development use visible absorbing photocatalysts (e.g., RuII or IrIII complexes, as well dyes) made light-induced convenient even non-photochemistry practitioners. It thus possible easily perform simply placing reaction vessel sunny place outside lab. However, these based single electron transfer (SET) (photoredox catalysis). Other able activate substrates via alternative paths, such hydrogen atom (HAT), emerging. In last years, we were deeply involved decatungstate anion ([W10O32]4-, polyoxometalate) synthesis. Indeed, versatile species promote photocatalytic C-H activation either SET HAT reactions. Interestingly, though spectrum [W10O32]4- does not extend into region, it shows an overlap with emission. Account, provide overview application salts window ledge chemistry. We initially discuss nature photogenerated mechanism action anion, also supported theoretical simulations. first-formed excited state decays rapidly active species, dark tagged wO, featuring presence electron-deficient oxygen centers. Next, describe applications significant part Account devoted photocatalyzed synthesis (C-X bond formation, X = C, N, O, oxidations) adopting sunlight (or simulated light). This synthetic approach versatile, cycloalkanes, alkylaromatics, amides, ethers (1,4-dioxane, oxetane, benzodioxole, THF), aldehydes, nitriles, cyclopentanones, ensuing addition resulting radicals onto olefins. Finally, increasing role water depollution polymerization briefly discussed.