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Metal-Free Approach to Biaryls from Phenols and Aryl Sulfoxides by Temporarily Sulfur-Tethered Regioselective C–H/C–H Coupling

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posted on 2016-10-30, 00:00 authored by Tomoyuki Yanagi, Shinya Otsuka, Yuko Kasuga, Keisuke Fujimoto, Kei Murakami, Keisuke Nogi, Hideki Yorimitsu, Atsuhiro Osuka
We have developed metal-free regiocontrolled dehydrogenative C–H/C–H cross-coupling of aryl sulfoxides with phenols by means of trifluoroacetic anhydride. Because the reaction would proceed through an interrupted Pummerer reaction followed by sulfonium-tethered [3,3]-sigmatropic rearrangement, the C–H/C–H coupling takes place exclusively between the ortho positions of both substrates. Various functional groups including carbonyl, halo, siloxy, and even boryl moieties are compatible. The biaryl products naturally possess hydroxy and sulfanyl groups, which allows the products to be useful synthetic intermediates, as evidenced by the syntheses of π-expanded heteroarenes such as unprecedented 7,12-dioxa[8]­helicene.

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