Review of 'Direct Nucleophilic Difluoromethylation of Aromatic Isoxazoles Activated by Electron-Withdrawing Groups Using (Difluoromethyl)trimethylsilane'

Direct difluoromethylation strategies are important for the pharmaceutical industry. This paper presents an elegant nucleophilic difluoromethylation strategy, that is complementary to the radical method recently developed by Baran et al (Nature 2012, 492, 95). The substrate scope of this new work is rather constrained at this early stage: the substrates have been chosen to be highly reactive towards nucleophiles, and a strongly electron-withdrawing group (eg NO2) is an absolute requirement, however an option is demonstrated for removing the NO2 group afterwards if desired. Yields in the nucleophilic difluoromethylation reactions are moderate, and diastereoselectivity ranges from poor to excellent. Experimentally, the set-up is reasonably straightforward although a glove-box is required. Compounds are characterised by H-NMR, C-NMR, F-NMR and low-res MS. Several biologically promising fluorinated heterocycles have been created in this work.