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Carbone G, O'Brien P, Hilmersson G. Asymmetric deprotonation using s-BuLi or i-PrLi and chiral diamines in THF: the diamine matters. J Am Chem Soc. 2010;132(43):15445-50doi: 10.1021/ja107672h.
Carbone, G., O'Brien, P., & Hilmersson, G. (2010). Asymmetric deprotonation using s-BuLi or i-PrLi and chiral diamines in THF: the diamine matters. Journal of the American Chemical Society, 132(43), 15445-50. https://doi.org/10.1021/ja107672h
Carbone, Giorgio, et al. "Asymmetric deprotonation using s-BuLi or i-PrLi and chiral diamines in THF: the diamine matters." Journal of the American Chemical Society vol. 132,43 (2010): 15445-50. doi: https://doi.org/10.1021/ja107672h
Carbone G, O'Brien P, Hilmersson G. Asymmetric deprotonation using s-BuLi or i-PrLi and chiral diamines in THF: the diamine matters. J Am Chem Soc. 2010 Nov 03;132(43):15445-50. doi: 10.1021/ja107672h. PMID: 20936816.
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J Am Chem Soc. 2010 Nov 03;132(43):15445-50. doi: 10.1021/ja107672h.

Asymmetric deprotonation using s-BuLi or i-PrLi and chiral diamines in THF: the diamine matters.

Journal of the American Chemical Society

Giorgio Carbone, Peter O'Brien, Göran Hilmersson

Affiliations

  1. Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.

PMID: 20936816 DOI: 10.1021/ja107672h

Abstract

The solution structures of [(6)Li]-i-PrLi complexed to (-)-sparteine and the (+)-sparteine surrogate in Et(2)O-d(10) and THF-d(8) at -80 °C have been determined using (6)Li and (13)C NMR spectroscopy. In Et(2)O, i-PrLi/(-)-sparteine is a solvent-complexed heterodimer, whereas i-PrLi/(+)-sparteine surrogate is a head-to-tail homodimer. In THF, there was no complexation of (-)-sparteine to i-PrLi until ≥3.0 equiv (-)-sparteine and with 6.0 equiv (-)-sparteine, a monomer was characterized. In contrast, the (+)-sparteine surrogate readily complexed to i-PrLi in THF, and with 1.0 equiv (+)-sparteine surrogate, complete formation of a monomer was observed. The NMR spectroscopic study suggested that it should be possible to carry out highly enantioselective asymmetric deprotonation reactions using i-PrLi or s-BuLi/(+)-sparteine surrogate in THF. Hence, three different asymmetric deprotonation reactions (lithiation-trapping of N-Boc pyrrolidine, an O-alkyl carbamate, and a phosphine borane) were investigated; it was shown that reactions with (-)-sparteine in THF proceeded with low enantioselectivity, whereas the corresponding reactions with the (+)-sparteine surrogate occurred with high enantioselectivity. These are the first examples of highly enantioselective asymmetric deprotonation reactions using organolithium/diamine complexes in THF.

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