Unlocking Photocatalytic Activity of Acridinium Salts by Anion‐Binding Co‐Catalysis
摘要:
The in situ generation of active photoredox organic catalysts upon anion‐binding co‐catalysis by making use of the ionic nature of common photosensitizers is reported. Hence, the merge of anion‐binding and photocatalysis permitted the modulation of the photocatalytic activity of simple acridinium halide salts, building an effective anion‐binding – photoredox ion pair complex able to promote a variety of visible light driven transformations, such as anti‐Markovnikov addition to olefins, Diels‐Alder and the desilylative C−C bond forming reactions. Anion‐binding studies, together with steady‐state and time‐resolved spectroscopy analysis, supported the postulated ion pair formation between the thiourea hydrogen‐bond donor organocatalyst and the acridinium salt, which proved essential for unlocking the photocatalytic activity of the photosensitizer.
A unique Markovnikov hydroalkoxylation of unactivated olefins with a cobalt complex, silane, and N-fluoropyridinium salt is reported. Further optimization of reaction conditions yielded high functional group tolerance and versatility of alcoholic solvent employed, including methanol, i-propanol, and t-butanol. Use of trifluorotoluene as a solvent made the use of alcohol in stoichiometric amount possible. Mechanistic insight into this novel catalytic system is also discussed. Experimental results suggest that catalysis involves both carbon radical and carbocation intermediates.
MASTRAL A. M.; BARLUENGA J., AFINIDAD, 1979, 36, NO 363, 401-404