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Abstract
1-Trimethyl-1-germylalkynes were synthesized by deprotonation of terminal alkynes with n-butyl lithium at low temperature followed by treatment with trimethylgermyl chloride under nitrogen atmosphere. The reagent system Cp2ZrCl2/2EtMgBr converts 1-trimethylgermyl-1-alkynes into α-trimethylgermylzirconacyclopentenes at -78 ºC for 1 h followed by stirring at room temperature overnight. These novel intermediates are hydrolyzed at 0 ºC for an hour to provide the corresponding (Z)-1-trimethylgermyl-1-alkenes in good yields (74-85%) and in high stereochemical purities (> 98%) as evidenced by 13C spectral data.
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References
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References
F. David-Quillot, S. Lunot, D. Marsacq and A. Duchêne, A Novel Access to Organogermanium Compounds, Tetrahedron Lett., 41, 4905 (2000); https://doi.org/10.1016/S0040-4039(00)00759-0
M. Lisbre, P. Mazerolles and J. Stage, The Organic Compounds of Germanium, Wiley: New York (1971).
S. Patai and Z. Rappoport, The Chemistry of Organic Germanium, Tin and Lead Compounds, Wiley: Chichester (1995).
T. Takahashi, Y. Nitto, T. Seki, M. Saburi and E. Negishi, Reaction of Dimethylzirconocene with Alkylmagnesium Halides as a Potentially General Method for Preparing Zirconocene-Alkene Complexes, Chem. Lett., 19, 2259 (1990); https://doi.org/10.1246/cl.1990.2259
T. Takahashi, N. Suzuki, M. Kageyama, Y. Nitto, M. Sabur and E. Negishi, Catalytic Hydrogenation of Alkenes Using Zirconocene–Alkene Complexes, Chem. Lett., 20, 1579 (1991); https://doi.org/10.1246/cl.1991.1579
A.A.A. Quntar, D. Rosenthal and M. Srebink, Synthesis of Novel 5-Hydroxyalkenylphosphonates by Addition of Aromatic Aldehydes to Zirconacyclopentenylphosphonates, Tetrahedron, 62, 5995 (2005); https://doi.org/10.1016/j.tet.2006.04.013
A.A. Aziz Quntar and M. Srebnik, Preparation of 5-Hydroxy-1-alkeny-boronates from 1-Alkynylboronates, Cp2ZrCl2/2EtMgBr and Aldehydes, Org. Lett., 6, 4243 (2004); https://doi.org/10.1021/ol0483504
N.G. Bhat and A. Garza, A Highly Diastereoselective Synthesis of (Z)-1-Trimethylgermyl-1-alkenes via the Hydroboration of 1-Trimethyl-germyl-1-alkynes Followed by Protonolysis, Synlett, 295 (2004); https://doi.org/10.1055/s-2004-815398