通过1,2-迁移过程可实现烯丙醇的电化学氧化双官能化,以合成β-三氟甲基酮。利用CF 3 SO 2 Na作为自由基源可以轻松获得一系列β-三氟甲基酮,而无需使用金属和牺牲性化学氧化剂。重要的是,该协议不仅实现了芳基迁移,而且还提供了烷基迁移产物。另外,电化学催化的环膨胀和克级反应证明了该方案的合成有用性。
NHC-Catalyzed Radical Trifluoromethylation Enabled by Togni Reagent
作者:Bei Zhang、Qiupeng Peng、Donghui Guo、Jian Wang
DOI:10.1021/acs.orglett.9b04203
日期:2020.1.17
An unprecedented carbene-catalyzed radical trifluoromethylation of olefins with aldehydes in the presence of Togni reagent was developed, thus providing the β-trifluoromethyl-α-substituted ketones with a broad scope and moderate to high chemical yields. Notably, this process includes a single-electron-transfer process and utilizes the persistent N-heterocyclic-carbene-bound radical as a key intermediate
Not only symmetrical, but also unsymmetrical α,α‐diaryl allylic alcohols are employed as substrates in the title reaction. A number of arenes and even heteroarenes underwent radical 1,2‐arylmigration (“neophyl rearrangement”) to produce α‐aryl β‐trifluoromethyl ketones. The preferential migration of electron‐deficient arylgroups over electron‐rich ones in unsymmetrical substrates supports the radical
Visible‐light‐enabled photocatalytic carbotrifluoro‐methylations of allylic alcohols and sodium triflinate were explored through 1,2‐migration of an aryl group, affording an efficient method for synthesis of β‐trifluoromethyl‐α‐substituted carbonyl compounds under mild reaction conditions. This catalyst system is well tolerant of various synthetically useful functional groups.
Iron-catalyzedtrifluoromethylation with concomitant 1,2-migration of an aryl group starting from diaryl allyl alcohol was achieved under mild conditions. This reaction system affords alpha-substituted-beta-trifluoromethyl carbonyl compounds in high efficiency. In the case of substrates bearing different aryl groups, selective migration was observed.