The nickel-mediated [3+2] cycloaddition of 2-trifluoromethyl-1-alkenes with alkynes afforded fluorine-containing multi-substituted cyclopentadienes in a regioselective manner. This reaction involves the consecutive two C-F bond cleavage of a trifluoromethyl or a pentafluoroethyl group through β-fluorine elimination.
Nickel-catalyzed [3 + 2] cycloaddition of 2-trifluoromethyl-1-alkenes with alkynes via domino C-F bond activation was achieved by sequential β-fluorine elimination. The nickel(ii) fluoride species formed in this reaction was reduced by a diboron compound, regenerating the catalytically active nickel(0) species.
Nucleophilic 5-endo-trig cyclisation of 2,2-difluorohomoallylic alcohols was achieved via allylic sp3 C–F bond activation to afford 3-fluoro-2,5-dihydrofurans.
The nickel-mediated [3+2] cycloaddition of 2trifluoromethyl-1-alkenes with alkynes afforded fluorine-containing multi-substituted cyclopentadienes in a regioselective manner. This reaction involves the consecutive two CÀF bond cleavage of a trifluoromethyl or a pentafluoroethyl group through b-fluorine elimination.
Scheme 1. CÀF bond activation by A) oxidative addition and B) bfluorine elimination.Scheme 2. Double CÀF bond activation of a CF 3 group by a) allylic CÀF bond activation via nickelacycles and b) intramolecular vinylic CÀF bond activation.
Die Kohlenstoff‐Fluor‐Bindung ist eine der stärksten chemischen Bindungen überhaupt und typischerweise schwer zu spalten. Eine Möglichkeit bieten metallvermittelte Ansätze unter Beteiligung einer oxidativen Addition. J. Ichikawa und Mitarbeiter präsentieren in ihrer Zuschrift auf eine neue Methode zur C‐F‐Bindungsspaltung, die eine β‐Fluor‐Eliminierung für eine nickelvermittelte [3+2]‐Cycloaddition nutzt. Das Titelbild zeigt zwei Werkzeuge für die Holzbearbeitung – eine Metallsäge (oxidative Addition) und ein Stemmeisen (β‐Eliminierung) – in Analogie zu den Methoden der metallvermittelten C‐F‐Bindungsspaltung.
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