1402817-48-4Relevant articles and documents
Titanium-catalyzed vinylic and allylic C-F bond activation-scope, limitations and mechanistic insight
Kuehnel, Moritz F.,Holstein, Philipp,Kliche, Meike,Krueger, Juliane,Matthies, Stefan,Nitsch, Dominik,Schutt, Joseph,Sparenberg, Michael,Lentz, Dieter
, p. 10701 - 10714 (2012)
The hydrodefluorination (HDF) of fluoroalkenes in the presence of a variety of titanium catalysts was studied with respect to scope, selectivity, and mechanism. Optimization revealed that the catalyst requires low steric bulk and high electron density; secondary silanes serve as the preferred hydride source. A broad range of substrates yield partially fluorinated alkenes, such as previously unknown (Z)-1,2-(difluorovinyl)ferrocene. Mechanistic studies indicate a titanium(III) hydride as the active species, which forms a titanium(III) fluoride by H/F exchange with the substrate. The HDF step can follow both an insertion/elimination and a σ-bond metathesis mechanism; the E/Z selectivity is controlled by the substrate. The catalysts' ineffieciency towards fluoroallenes was rationalized by studying their reactivity towards Group 6 hydride complexes. The broad application of the catalytic hydrofluorination of fluoroalkenes by the system [Cp2TiF 2]/silane is demonstrated. Isolated yields up to 79 % could be obtained for various substrates. Mechanistic studies indicate two competing reaction mechanisms. Copyright
