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Lewis Acid Mediated [2,3]-Sigmatropic Rearrangement of Allylic Ammonium Ylides
KTH, Superseded Departments, Chemistry.
KTH, Superseded Departments, Chemistry.
2003 (English)In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 44, no 15, 3159-3162 p.Article in journal (Refereed) Published
Abstract [en]

An investigation of the Lewis acid mediated [2,3]-sigmatropic rearrangement of allylic ammonium ylides has been conducted by employing various bases and boron Lewis acids. Using BBr3 together with the phosphazene base 6, various allylic amines could be rearranged in good yields with low to excellent diastereoselectivity.

Place, publisher, year, edition, pages
2003. Vol. 44, no 15, 3159-3162 p.
Keyword [en]
[2, 3]-sigmatropic rearrangement, ammonium ylide, Lewis acid
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-6872DOI: 10.1016/S0040-4039(03)00510-0ISI: 000181978800032OAI: oai:DiVA.org:kth-6872DiVA: diva2:11704
Note
QC 20100921Available from: 2005-09-27 Created: 2005-09-27 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Asymmetric [2,3]-Sigmatropic Rearrangement of Allylic Ammonium Ylides
Open this publication in new window or tab >>Asymmetric [2,3]-Sigmatropic Rearrangement of Allylic Ammonium Ylides
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The thesis describes the realization of an asymmetric [2,3]-sigmatropic rearrangement of achiral allylic amines. It is divided into two parts; the first part deals with the development of a Lewis acid-mediated [2,3]-sigmatropic rearrangement and the second the asymmetric version thereof. Quaternization of an -amino amide with various Lewis acids established BBr3 and BF3 to be the most appropriate ones. Various allylic amines were subsequently rearranged into the corresponding homoallylic amines in good to excellent syn-diastereoselectivities, revealing the endo-transition state to be the preferred pathway. The structures of the intermediate Lewis acid-amine complexes were confirmed by NMR spectroscopy studies and DFT calculations.

Based on this investigation a chiral diazaborolidine was chosen as Lewis acid and was shown to efficiently promote the asymmetric [2,3]-sigmatropic rearrangement furnishing homoallylic amines in good yields and excellent enantiomeric excesses. In contrast to the achiral rearrangement mediated by BBr3 and BF3, the asymmetric version gave the opposite major diastereomer, revealing a preference for the exo-transition state in the asymmetric rearrangement. To account for the observed selectivities, a kinetic and thermodynamic pathway was presented. On the basis of a deuterium exchange experiment on a rearranged Lewis acid-amine complex and an NMR spectroscopic investigation, the kinetic pathway was shown to be favored.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 68 p.
Series
Trita-IOK, ISSN 1100-7974 ; 2005:97
Keyword
asymmetric, [2, 3]-sigmatropic rearrangement, allylic amine, ammonium ylide, Lewis acid, enantioselective, boron, phosphazene base, NMR spectroscopy, DFT-calculations
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-430 (URN)91-7178-135-8 (ISBN)
Public defence
2005-10-07, Salongen, KTHB, KTH, Stockholm, 09:00
Opponent
Supervisors
Note
QC 20100927Available from: 2005-09-27 Created: 2005-09-27 Last updated: 2010-09-27Bibliographically approved

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