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Armstrong DR, Harris CM, Kennedy AR, et al. Developing lithium chemistry of 1,2-dihydropyridines: from kinetic intermediates to isolable characterized compounds. Chemistry. 2015;21(41):14410-20doi: 10.1002/chem.201501880.
Armstrong, D. R., Harris, C. M., Kennedy, A. R., Liggat, J. J., McLellan, R., Mulvey, R. E., Urquhart, M. D., & Robertson, S. D. (2015). Developing lithium chemistry of 1,2-dihydropyridines: from kinetic intermediates to isolable characterized compounds. Chemistry (Weinheim an der Bergstrasse, Germany), 21(41), 14410-20. https://doi.org/10.1002/chem.201501880
Armstrong, David R, et al. "Developing lithium chemistry of 1,2-dihydropyridines: from kinetic intermediates to isolable characterized compounds." Chemistry (Weinheim an der Bergstrasse, Germany) vol. 21,41 (2015): 14410-20. doi: https://doi.org/10.1002/chem.201501880
Armstrong DR, Harris CM, Kennedy AR, Liggat JJ, McLellan R, Mulvey RE, Urquhart MD, Robertson SD. Developing lithium chemistry of 1,2-dihydropyridines: from kinetic intermediates to isolable characterized compounds. Chemistry. 2015 Oct 05;21(41):14410-20. doi: 10.1002/chem.201501880. Epub 2015 Aug 31. PMID: 26333094.
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Chemistry. 2015 Oct 05;21(41):14410-20. doi: 10.1002/chem.201501880. Epub 2015 Aug 31.

Developing lithium chemistry of 1,2-dihydropyridines: from kinetic intermediates to isolable characterized compounds.

Chemistry (Weinheim an der Bergstrasse, Germany)

David R Armstrong, Catriona M M Harris, Alan R Kennedy, John J Liggat, Ross McLellan, Robert E Mulvey, Matthew D T Urquhart, Stuart D Robertson

Affiliations

  1. WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL (UK).
  2. WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL (UK). [email protected].
  3. WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL (UK). [email protected].

PMID: 26333094 DOI: 10.1002/chem.201501880

Abstract

Generally considered kinetic intermediates in addition reactions of alkyllithiums to pyridine, 1-lithio-2-alkyl-1,2-dihydropyridines have been rarely isolated or characterized. This study develops their "isolated" chemistry. By a unique stoichiometric (that is, 1:1, alkyllithium/pyridine ratios) synthetic approach using tridentate donors we show it is possible to stabilize and hence crystallize monomeric complexes where alkyl is tert-butyl. Theoretical calculations probing the donor-free parent tert-butyl species reveal 12 energetically similar stereoisomers in two distinct cyclotrimeric (LiN)3 conformations. NMR spectroscopy studies (including DOSY spectra) and thermal volatility analysis compare new sec-butyl and iso-butyl isomers showing the former is a hexane soluble efficient hydrolithiation agent converting benzophenone to lithium diphenylmethoxide. Emphasizing the criticalness of stoichiometry, reaction of nBuLi/Me6 TREN with two equivalents of pyridine results in non-alkylated 1-lithio-1,4-dihydropyridine⋅Me6 TREN and 2-n-butylpyridine, implying mechanistically the kinetic 1,2-n-butyl intermediate hydrolithiates the second pyridine.

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

Keywords: hydrides; lithium; nucleophilic addition; pyridine; structure elucidation

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