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Synthesis of 2‑Aryl Acetophenones via Hydrobromination and Oxy-isomerization of (o‑Arylethynyl)benzyl Alcohols

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journal contribution
posted on 14.04.2021, 19:45 by Tzu-Hsuan Kuan, Duen-Ren Hou
Hydrobromination and oxy-isomerization of (o-arylethynyl)­benzyl alcohols to yield brominated aryl ketones were achieved with bromotrimethylsilane. The substrate scope suggested that vinyl carbocations, stabilized by the conjugated aryl groups, are the reaction intermediates. 1H-Isochromene was also detected by 1H NMR, and an isolated 1H-isochromene was converted to the product when retreated with TMSBr. The formation of 1H-isochromene is equivalent to a 6-endo-dig cyclization and contrasts with the corresponding reactions under basic conditions, in which the 5-exo-dig process dominated.