Читать книгу Organofluorine Chemistry - Группа авторов - Страница 11

In the abovementioned water‐promoted trifluoromethylation, a stoichiometric amount of copper is required and gem‐difluoroolefin was found to be formed under strictly anhydrous conditions. Inspired by this fact, we developed a copper‐catalyzed gem‐difluoroolefination of diazo compounds, concisely [15] (Scheme 1.2a). In this catalytic reaction, diaryl diazomethanes were used instead of α‐diazo esters for two reasons: (i) diaryl diazomethanes possess higher reactivity than α‐diazo esters and can react with unactivated “CuCF₃” directly (without the need for eliminating ligated iodide in “CuCF₃”), making the addition of excess water or CuI as iodide scavenger no longer necessary, and (ii) diaryl‐substituted alkylcopper intermediate 2 readily undergoes β‐fluoride elimination (even in the presence of excess amount of water) (Scheme 1.2b), which is critical to regenerate the copper catalyst and close the catalytic cycle.

Scheme 1.2 Copper‐catalyzed gem‐difluoroolefination of diazo compounds.