Togni Reagent: A Hypervalent Iodine Based Electrophilic Trifluoromethylation Reagent

Abstract

Antonio Togni and co-workers have [¹] reported a new electrophilic trifluoromethylating reagent based on a 10-I-3 hypervalent iodine, 3,3-dimethyl-1-(trifluoromethyl)-1,2-benziodoxole known as Togni reagent 1, which nicely complements the nucleophilic Ruppert-Prakash reagent. [²] The Togni reagent has the ability to transfer a CF3 moiety electophilically to a wide range of substrates and functionalities, including C=C and C-H bonds in hydrocarbons as well as atoms containing lone pairs, such as sulfide, primary and secondary alcohols. This electrophilic CF3 transfer agent is the reagent of choice for most trifluoro­methylation reactions (better than Yagupol’skii, [³] Umemoto, [4-8] and Shreeve [9] reagents) due to its substrate-induced selectivity, specificity, high reactivity under mild conditions (at 0-25 ˚C and neutral pH), and applicability to acid- or base-sensitive substrates. It is easy to handle and can be exposed to moist air for short periods of time without any apparent alteration.