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

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.

本研究团队成功研发了一种不含金属的区域选择性脱氢偶联反应，该反应通过三氟乙酸酐将芳基硫氧烷与酚类化合物进行交叉偶联。由于反应过程涉及中断的普默尔反应，随后通过磺酰基连接的[3,3]-σ键重排，碳-氢/碳-氢偶联仅发生在两种底物的邻位位置。包括羰基、卤素、硅氧基甚至硼基在内的多种官能团均能与该方法兼容。生成的双芳基产物自然含有羟基和硫烷基，这使得产物可作为有用的合成中间体，如合成π扩展杂环化合物，如前所未有的7,12-二氧[8]螺旋烯等实例所证实。