Single C–F Transformations of o-Hydrosilyl Benzotrifluorides with Trityl Compounds as All-in-One Reagents

Abstract

A facile method to prepare difluoromethylenes, including α,αdifluorobenzyl chlorides, by single C−F transformations of benzotrifluorides is disclosed. The C−F cleavage followed by chlorination proceeded smoothly using trityl chloride through the generation of trityl cation as an activator and chloride anion as a nucleophile. Diverse difluoromethylenes such as difluorobenzyl ethers were efficiently prepared by virtue of the good versatility of the resulting chloro and fluorosilyl groups. Letter pubs.acs.org/OrgLett

Recent Advances in the Synthesis of Difluorinated Architectures from Trifluoromethyl Groups

“…Based on this work, they discovered a facile method for the preparation of difluoromethylenes by the single CÀ F bond cleavage of o-hydrosilyl benzotrifluorides 7 (Scheme 3). [12] CÀ F cleavage followed by chlorination using trityl chloride 10 through the formation of trityl cation 11 as an activator and chloride anion as a nucleophile proceeds smoothly. A concerted mechanism, including hydride abstraction and CÀ F bond cleavage, may be involved in both protocols.…”

C-F bond activation under transition-metal-free conditions

“…Interestingly, Tobisu's group [110] reported a phosphinecatalyzed intermolecular acylfluorination of alkynes using acyl fluorides as the fluorinating reagents (Scheme 40). Halogen groups (207) were compatible in the reactions. The ratio of isomers was determined under thermodynamic.…”

“…A o-hydrosilyl-assisted C-F transformation was developed by Yoshida's group [207] (Scheme 85). Utilizing in-situ generated trityl cation as the activator and the counter cation as the nucleophile, various transformations from C−F to C−Cl, C−Br, C−OTs, and C−SCN were achieved (475-480).…”

FLP-Catalyzed Monoselective C–F Functionalization in Polyfluorocarbons at Geminal or Distal Sites

“…Several methods have been developed to overcome “over-reaction” in polyfluorocarbons with equivalent geminal fluoro-positions (challenge 1, Figure A), but most methods are specific to certain substrates. For example, trifluormethylarenes with ortho -silyl groups allow the nucleophilic substitution of a single fluoride, and electron-poor trifluoromethylarenes allow single-electron transfer (SET)-mediated selective defluoroalkylation . In CF 2 X groups (X = H, F) with vicinal keto or olefin positions, selective functionalization can be achieved through the formation of sp 2 C–F bonds in the products that are thermodynamically more stable than sp 3 C–F bonds …”