Asymmetric ammonium ylid rearrangements: the effect of nitrogen asymmetry
Sweeney, J.B., Tavassoli, A. and Workman, J.A. (2006) Asymmetric ammonium ylid rearrangements: the effect of nitrogen asymmetry. Tetrahedron, 62 (49). pp. 11506-11512. ISSN 0040-4020
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To link to this article DOI: 10.1016/j.tet.2006.06.043
[2,3]-Sigmatropic rearrangements of allylic ammonium ylids derived from glycinoylcamphorsultams are highly selective in terms of relative and absolute stereocontrol only when acyclic alkenes are present. When chiral esters of ylids derived from N-methyltetrahydro-pyridine ('NMTP') undergo rearrangement, the reactions show exclusive cis-stereoselectivity but the products are obtained with virtually no absolute stereocontrol. These observations support the notion that sigmatropic rearrangements of N-chiral ammonium ylids are controlled by nitrogen stereogenicity. (c) 2006 Elsevier Ltd. All rights reserved.