Trifluoromethoxylation of arenes: synthesis of ortho-trifluoromethoxylated aniline derivatives by OCF3 migration.

Aryl trifluoromethoxylation by a two-step sequence of O-trifluoromethylation of N-aryl-N-hydroxylamine derivatives and intramolecular OCF3  migration is presented. This protocol allows easy access to a wide range of synthetically useful ortho-OCF3 aniline derivatives. In addition, it utilizes bench-stable reagents, is operationally simple, shows high functional-group tolerance, and is amenable to gram-scale as well as one-pot synthesis. A reaction mechanism of a heterolytic cleavage of the NOCF3 bond followed by recombination of the resulting nitrenium ion and trifluoromethoxide is proposed for the OCF3 -migration reaction.

Pd-catalyzed aryl C-H imidation with arene as the limiting reagent.

An amine-N-oxide-ligated palladium complex, in conjunction with a silver cocatalyst, catalyzes imidation of arenes by the reagent N-fluorobenzenesulfonimide. The reaction enables imidation of a variety of arenes at or below room temperature, requires no coordinating directing group on the substrate, and gives synthetically useful yields with only 1 equiv of arene. Mechanistic data implicate an unusual mechanism devoid of commonly invoked organometallic intermediates: oxidation of the Pd catalyst occurs as the turnover-limiting step, while C-H bond functionalization occurs subsequently at a high oxidation state of the catalyst.