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Intemann J, Bauer H, Pahl J, et al. Calcium Hydride Catalyzed Highly 1,2-Selective Pyridine Hydrosilylation. Chemistry. 2015;21(32):11452-61doi: 10.1002/chem.201501072.
Intemann, J., Bauer, H., Pahl, J., Maron, L., & Harder, S. (2015). Calcium Hydride Catalyzed Highly 1,2-Selective Pyridine Hydrosilylation. Chemistry (Weinheim an der Bergstrasse, Germany), 21(32), 11452-61. https://doi.org/10.1002/chem.201501072
Intemann, Julia, et al. "Calcium Hydride Catalyzed Highly 1,2-Selective Pyridine Hydrosilylation." Chemistry (Weinheim an der Bergstrasse, Germany) vol. 21,32 (2015): 11452-61. doi: https://doi.org/10.1002/chem.201501072
Intemann J, Bauer H, Pahl J, Maron L, Harder S. Calcium Hydride Catalyzed Highly 1,2-Selective Pyridine Hydrosilylation. Chemistry. 2015 Aug 03;21(32):11452-61. doi: 10.1002/chem.201501072. Epub 2015 Jun 26. PMID: 26120024.
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Chemistry. 2015 Aug 03;21(32):11452-61. doi: 10.1002/chem.201501072. Epub 2015 Jun 26.

Calcium Hydride Catalyzed Highly 1,2-Selective Pyridine Hydrosilylation.

Chemistry (Weinheim an der Bergstrasse, Germany)

Julia Intemann, Heiko Bauer, Jürgen Pahl, Laurent Maron, Sjoerd Harder

Affiliations

  1. Stratingh Institute for Chemistry, Nijenborgh 4, 9747AG Groningen (The Netherlands).
  2. Friedrich-Alexander University Erlangen-Nürnberg, Inorganic and Organometallic Chemistry, Egerlandstraße 1, 91058 Erlangen (Germany).
  3. Université de Toulouse et CNRS INSA, UPS, CNRS, UMR 5215, LPCNO, 135 avenue de Rangueil, 31077 Toulouse (France).

PMID: 26120024 DOI: 10.1002/chem.201501072

Abstract

Reaction of the calcium hydride complex (DIPPnacnac-CaH⋅THF)2 with pyridine is much faster and selective than that of the corresponding magnesium hydride complex (DIPPnacnac = [(2,6-iPr2 C6 H3 )NC(Me)]2 CH). With a range of pyridine, picoline and quinoline substrates, exclusive transfer of the hydride ligand to the 2-position is observed and also at higher temperatures no 1,2→1,4 isomerization is found. The heteroleptic product DIPPnacnac-Ca(1,2-dihydropyridide)⋅(pyridine) shows fast ligand exchange into homoleptic calcium complexes and therefore could not be isolated. Calcium hydride reduction of isoquinoline gave well-defined homoleptic products which could be characterized by X-ray diffraction: Ca(1,2-dihydroisoquinolide)2 ⋅(isoquinoline)4 and Ca3 (1,2-dihydroisoquinolide)6 ⋅(isoquinoline)6 . The striking selectivity difference in the dearomatization of pyridines by Mg or Ca complexes could be explained by DFT theory and was utilized in catalysis. Whereas hydroboration of pyridine with pinacol borane with a calcium hydride catalyst gave only minor conversion, the hydrosilylation of pyridine and quinolines with PhSiH3 yields exclusively 1,2-dihydropyridine and 1,2-dihydroquinoline silanes with 80-90 % conversion. Similar results can be achieved with the catalyst Ca[N(SiMe3 )2 ]2 ⋅(THF)2 . These calcium complexes represent the first catalysts for the 1,2-selective hydrosilylation of pyridines.

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Keywords: calcium; catalysis; hydride; hydrosilylation; reduction

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