The Formation of a Mixed Organolithium Aggregate Li4R2nBu2 during the Heteroatom-Assisted Lithiation of 1,3-Bis(dimethylaminomethyl)-2,4,6-trimethylbenzene (R = 2,6-(CH2NMe2)2-3,5-Me2C6HCH2)†
Peter Wijkens
Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, NL-3584 CH Utrecht (The Netherlands) Telefax: Int. code +(30) 523-615
Search for more papers by this authorErnout M. van Koten
Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, NL-3584 CH Utrecht (The Netherlands) Telefax: Int. code +(30) 523-615
Search for more papers by this authorMaurits D. Janssen
Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, NL-3584 CH Utrecht (The Netherlands) Telefax: Int. code +(30) 523-615
Search for more papers by this authorDr. Johann T. B. H. Jastrzebski
Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, NL-3584 CH Utrecht (The Netherlands) Telefax: Int. code +(30) 523-615
Search for more papers by this authorDr. Anthony L. Spek
Bijvoet Center for Biomolecular Research Laboratory of Crystal and Structural Chemistry, Utrecht University
Search for more papers by this authorCorresponding Author
Prof. Dr. Gerard van Koten
Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, NL-3584 CH Utrecht (The Netherlands) Telefax: Int. code +(30) 523-615
Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, NL-3584 CH Utrecht (The Netherlands) Telefax: Int. code +(30) 523-615Search for more papers by this authorPeter Wijkens
Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, NL-3584 CH Utrecht (The Netherlands) Telefax: Int. code +(30) 523-615
Search for more papers by this authorErnout M. van Koten
Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, NL-3584 CH Utrecht (The Netherlands) Telefax: Int. code +(30) 523-615
Search for more papers by this authorMaurits D. Janssen
Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, NL-3584 CH Utrecht (The Netherlands) Telefax: Int. code +(30) 523-615
Search for more papers by this authorDr. Johann T. B. H. Jastrzebski
Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, NL-3584 CH Utrecht (The Netherlands) Telefax: Int. code +(30) 523-615
Search for more papers by this authorDr. Anthony L. Spek
Bijvoet Center for Biomolecular Research Laboratory of Crystal and Structural Chemistry, Utrecht University
Search for more papers by this authorCorresponding Author
Prof. Dr. Gerard van Koten
Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, NL-3584 CH Utrecht (The Netherlands) Telefax: Int. code +(30) 523-615
Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, NL-3584 CH Utrecht (The Netherlands) Telefax: Int. code +(30) 523-615Search for more papers by this authorDedicated to Professor Ekkehard Lindner on the occasion of his 60th birthday
Graphical Abstract
Lithiated 1 and unreacted n-butyllithium in a 2:2 ratio make up the title aggregate 2, which is formed in the reaction of 1 with two equivalents of n-butyllithium (shown below). Species such as 2 can be regarded as intermediates in heteroatom-facilitated lithiation reactions.
References
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- 8 With this knowledge in mind, it is obvious that reaction of 1 with 2 equiv of n BuLi would afford 2 in quantitative yield (see Experimental Procedure).
- 9
X-ray crystal structure data for 2: C38H68Li4N4, monoclinic, space group P21/c, a = 10.8476(7), b = 16.5638(11), c = 22.3064(12) Å, β = 101.525(5)°, V = 3927.1(4) Å3, Pcalcd = 1.030 gcm−3, μ(MoKα) = 0.5 cm−1, Z = 4, 8946 unique reflections (1.5 < θ < 27.4), 3800 with F0 > 4.0σ(F0). Enraf-Nonius CAD4T rotating anode diffractometer, graphite monochromated MoKα radiation, λ = 0.7 1073 Å, T = −123 °C. Solution by direct methods (SHELXS86), refinement of F2 with SHELXL-93 converged at R1 (wR2) = 0.088 (0.242), w = 1/(σ2(F
) + (0.1124P)2) for 416 refined parameters (anisotropic temperature factors for the nonhydrogen atoms). Hydrogen atoms were included at calculated positions (CH = 0.98 Å), riding on their carrier atoms. Further details of the crystal structure investigation are available on request from the Cambridge Crystallographic Data Centre, University Chemical Laboratory, 12 Union Road, Cambridge CB2 1EZ (UK), on quoting the full journal citation.
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- 22
However, in the case of the present benzylic diamine chelate the \documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${\rm Li}_4{\rm Bu}_2({\mathop{\rm C\,N}\limits^{\frown}}_2)_2$\end{document}
aggregate is further stabilized, since the two \documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${\mathop{\rm C\,N}\limits^{\frown}}_2$\end{document}
groups effectively cap the four Li atoms and prevent further attack by the free benzylic diamine ligands.
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- 24 Obtained in almost quantitative yield by reaction of 1,3-bis(bromomethyl)-2,4,6-trimethylbenzene [25] with 4 equiv of Me2NH: characterized by 1H and 13C NMR spectroscopy and GCMS.
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- 26 Detailed 1H, 13C, and 6Li NMR data are available upon request from the authors.
