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Lewis Acid Mediated [2,3]-Sigmatropic Rearrangement of Allylic alpha-Amino Amides
KTH, Superseded Departments, Chemistry.
KTH, Superseded Departments, Chemistry.
2004 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 69, no 9, 3043-3049 p.Article in journal (Refereed) Published
Abstract [en]

 Boron trifluoride and BBr3 mediated [2,3]-sigmatropic rearrangements of allylic alpha-amino amides have been developed affording secondary amines in good yields. (E)-Crotyl and (E)-cinnamyl alpha-amino amides 2b and 2c exhibit excellent syn-diastereoselectivity upon rearrangement with either Lewis acid. The allylic amine 2a forms upon treatment with BF3 or BBr3 a five-membered heterocylic complex in which a single halide anion has been displaced by the carbonyl oxygen atom. The structures of the Lewis acid-amine complexes were elucidated using NMR spectroscopy. A plausible reaction mechanism, based on DFT calculations, is presented. Thus, BF3- or BBr3-complexed allylic amines 2 are shown to preferentially proceed, after deprotonation, via an endo transition state.

Place, publisher, year, edition, pages
2004. Vol. 69, no 9, 3043-3049 p.
Keyword [en]
Complexation, Nuclear magnetic resonance spectroscopy, Oxygen, Probability density function, Reaction kinetics, Stereochemistry
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-6873DOI: 10.1021/jo035618gISI: 000221268200017Scopus ID: 2-s2.0-2142659321OAI: oai:DiVA.org:kth-6873DiVA: diva2:11705
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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