Difluorocarbene Generation from TMSCF3: Kinetics and Mechanism of NaI-Mediated and Si-Induced Anionic Chain Reactions

• DOI: 10.1021/jacs.0c06751
• Publication Date: 2020-07-27T15:31:12Z
• Authors: Andrés García-Dom...; Thomas H. West; Johann J. Primozic; Katie M. Grant; Craig P. Johnston; Grant G. Cumming; Andrew G. Leach; Guy C. Lloyd-Jones
• Keywords: Difluorocarbene; Alkene; Reactive intermediate

The mechanism of CF2 transfer from TMSCF3 (1), mediated by TBAT (2–12 mol %) or NaI (5–20 %), has been investigated in situ/stopped-flow 19F NMR spectroscopic analysis the kinetics alkene difluorocyclopropanation and competing TFE/c-C3F6/homologous perfluoroanion generation, 13C/2H KIEs, LFERs, efficiency selectivity, effect inhibitors, density functional theory (DFT) calculations. reactions evolve with profoundly different kinetics, undergoing autoinhibition (TBAT) quasi-stochastic autoacceleration (NaI) cogenerating perfluoroalkene side products. An overarching involving direct indirect fluoride a CF3 anionoid to (1) elucidated. It allows rationalization why NaI-mediated process is more effective for less-reactive alkenes alkynes, large excess required all cases, slow-addition protocols can be benefit. Issues relating exothermicity, toxicity, scale-up are also noted.