The stereochemistry of aziridine borane lithiation: diastereoselectivity and enantioselectivity |
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Authors: | E Vedejs A.S Bhanu PrasadJ.T Kendall J.S Russel |
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Affiliation: | a Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA b Department of Chemistry, University of Wisconsin, Madison, WI 53706, USA |
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Abstract: | Lithiation of 1-methylaziridine borane, 1-(tert-butyldimethylsiloxyethyl)aziridine borane, or 1-(tert-butyldimethylsiloxyethyl)-2-methylaziridine borane occurs syn to the boron substituent, while lithiation of 1-(tert-butyldimethylsiloxyethyl)-2-trimethylstannylaziridine borane occurs anti to boron as well as silicon due to the steric effect of trimethylsilyl group (s-butyllithium was used in all cases). Kinetically controlled lithiation in the first three cases results from a combination of steric and electrostatic effects. Enantioselective lithiation occurs in the presence of (−)-sparteine, with product enantioselectivities near 70% ee. |
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Keywords: | 2-lithioaziridine aziridine enantioselective lithiation sparteine |
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