Synthesis of the Smallest Axially Chiral Molecule by Asymmetric Carbon-Fluorine Bond Activation
作者:Moritz F. Kuehnel、Tobias Schlöder、Sebastian Riedel、Belén Nieto-Ortega、Francisco J. Ramírez、Juan T. López Navarrete、Juan Casado、Dieter Lentz
DOI:10.1002/anie.201108105
日期:2012.2.27
Enantioselect‐DeFluor: Carbon–fluorinebond cleavage by a chiral zirconium complex allows the synthesis of optically active 1,3‐difluoroallene for the first time. Its absolute configuration was established by gas‐phase vibrational circular dichroism spectroscopy (see picture).
C−D<sub>0</sub> (D<sub>0</sub> = π-donor, F) Cleavage in H<sub>2</sub>CCH(D<sub>0</sub>) by (Cp<sub>2</sub>ZrHCl)<i><sub>n</sub></i>: Mechanism, Agostic Fluorines, and a Carbene of Zr(IV)
作者:Lori A. Watson、Dmitry V. Yandulov、Kenneth G. Caulton
DOI:10.1021/ja0024340
日期:2001.1.1
Consistent with the C-O cleavage behavior of vinyl ethers, vinyl fluoride reacts with Cp2ZrHCl to give Cp2ZrFCl and C2H4 as primary; products. DFT (B3PW91) calculations show this reaction to be highly exoenergetic (-55 kcal/mol), and reveal a sigma -bond metathesis mechanism to be unfavorable compared to a Zr-H addition across the C=C bond, with regiochemistry placing F on C-beta of the resulting fluoroethyl ligand. beta -F elimination (onto Zr)then completes the reaction. There is no eta (2)-olefin intermediate on the reaction path. DFT calculations seeking the energy and: structure of the two carbenes Cp2ZrHCl[CF(CH3)] and Cp2ZrFCl[CH(CH3)] are also described.