Dearomatization Approach to 2‑Trifluoromethylated Benzofuran and Dihydrobenzofuran Products

A mild dearomatization enabled ortho-selective
replacement of an aromatic C–H bond with a hexafluoro­acetylacetone
(hfacac) substituent has been developed. This reaction is dependent
on a hypervalent iodine generated phenoxonium intermediate, a critical
choice of solvent, and reagent addition order. The fluorinated dihydrobenzofuran
product can be transformed into dihydrobenzofuran and benzofuran products
decorated with a 2-trifluoromethyl group. The 3-trifluoro­methylacyl
substituted benzofurans rapidly form hydrates, which can be reduced
to the corresponding alcohols.

本研究开发了一种温和脱芳构化驱动的、以六氟乙酰丙酮（hexafluoroacetylacetone, hfacac）取代基实现芳香族C-H键邻位选择性取代的反应。该反应的关键依赖条件包括高价碘介导生成的苯氧鎓中间体、溶剂的精准选择以及试剂的加料顺序。所得氟化二氢苯并呋喃产物可进一步转化为带有2-三氟甲基取代基的二氢苯并呋喃与苯并呋喃产物。带有3-三氟甲基酰基取代基的苯并呋喃可快速形成水合物，该类水合物可被还原为相应的醇类化合物。