On the reason for opposite diastereoselectivities of benzyllithium compounds containing lithium amide and lithium alkoxide functionalities

The carbolithiation of N-methyl-3-phenyl-prop-2-enylamine with tert-butyllithium leads to the monomeric benzyllithium compound 7 in good yield. The consecutive reaction with electrophiles exhibits a high anti diastereoselectivity, opposite to what has been earlier found for the oxygen analogue 3. PM...

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Bibliographic Details
Published in:Tetrahedron 1996-07, Vol.52 (30), p.10025-10042
Main Authors: Mück-Lichtenfeld, Christian, Ahlbrecht, Hubertus
Format: Article
Language:English
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Summary:The carbolithiation of N-methyl-3-phenyl-prop-2-enylamine with tert-butyllithium leads to the monomeric benzyllithium compound 7 in good yield. The consecutive reaction with electrophiles exhibits a high anti diastereoselectivity, opposite to what has been earlier found for the oxygen analogue 3. PM3 semiempirical calculations on the intermediates show a preference of the anti configuration which is confirmed by 1H NMR. Measurements of the degree of aggregation show the dilithio compound 3 to exist as a dimer and higher aggregates in THF. PM3 calculations on this dimer can explain the different diastereoselectivity. Graphic
ISSN:0040-4020
1464-5416
DOI:10.1016/0040-4020(96)00535-2