Copper-Catalyzed C(sp³)–C(sp³) Bond Formation Using a Hypervalent Iodine Reagent: An Efficient Allylic Trifluoromethylation

Abstract

An efficient copper-catalyzed allylic trifluoromethylation reaction has been developed. This reaction provides a general and straightforward way to synthesize allylic trifluoromethylated compounds under mild conditions.

Recent progress in the trifluoromethylation of alkenes with Togni's reagents

“…In 2011, the groups of Buchwald 23 and Wang 24 showed that Togni's reagents can be used as a clean source of the CF 3 radical for the trifluoromethylation of alkenes. These trifluoromethylations rely on Cu(I) catalysis, and experimental evidence for the involvement of free CF 3 radicals was provided (Scheme 2).…”

“…A proposed mechanism for this trifluoromethylation reaction is depicted in Scheme 3. Reaction of Togni's reagents with a copper catalyst generates a CF 3 radical (Scheme 2), 23,24 followed by radical addition and single-electron oxidation to give intermediate C. 26 Subsequent trapping of the carbocation C with a nucleophile leads to the desired product D. It is assumed that trifluoromethylation of olefin substrate E might be achieved using a copper-based strategy involving the generation of an allylic radical and a subsequent CF 3 transfer (Scheme 3, Path A). [27][28][29] Alternatively, if Togni's reagent 1 could be used as an electrophilic CF 3 ·equivalent, the final product F may be generated through an atom transfer radical addition type pathway (Scheme 3, Path B).…”

“…24 The simple alkenes, aliphatic aldehyde group, and tert-butyldimethylsilyl (TBDMS) ether protecting group were tolerated in the reaction, with the desired product being obtained in excellent yield. …”

Recent advances in green fluorine chemistry

“…In 2011, Parsons et al, 84 Xu et al, 85 and Wang et al 86 reported the trifluoromethylation of unactivated olefins with a copper(I) salt and either Umemoto or Togni reagent ( Figure 39). Although these reactions provide accesses to compounds bearing CF 3 at allylic positions, these transformations are restricted to monosubstituted terminal olefins.…”

Recent Advances of Trifluoromethylation

“…12), 该方法可应用于向复杂分子的 芳环引入三氟甲基(如 Estrone 和 Vitamin E 等). 2011 年, 清华大学刘磊教授 [42] 和北京大学的王剑 波教授等 [43] 发现在铜催化下, 亲电三氟甲基化试剂与 未活化的烯烃反应可生成三氟甲基化的烯丙基化合物 (Scheme 13), 他们对反应机理也进行了探索. [26] , Hartwig [21] 和 Gooβen 等 [25] 进一步开展硼酸和硼酯的氧化三氟甲基 化反应; 刘磊 [38] 、沈其龙 [39] 和肖吉昌等 [40] 研究了芳基硼 酸与亲电三氟甲基化试剂的反应.…”