Issue 2, 2017

Mechanistic insight into the acid-catalyzed isomerization of biomass-derived polysubstituted pyrrolidines: an experimental and DFT study

Abstract

The 1,3-dipolar cycloaddition reactions of azomethine ylides is one of the preferred methods for the synthesis of polysubstituted pyrrolidines. The use of chiral dipolarophiles derived from carbohydrates yields enantiomerically pure pyrrolidines, usually in good to excellent endo selectivities, along with other minor stereoisomers. Recently, we found an unusual isomerization event that allowed the isolation of useful pyrrolidines with relative stereochemistries difficult to obtain otherwise. Although a simple and efficient protocol to promote these transformations was developed, the mechanism was not fully unravelled. Herein, after a combination of experimental, spectroscopic and computational studies (using DFT methods) we propose that this isomerization event takes place through a retro-Mannich//Mannich cascade, via the formation of an iminium ion with E geometry.

Graphical abstract: Mechanistic insight into the acid-catalyzed isomerization of biomass-derived polysubstituted pyrrolidines: an experimental and DFT study

Supplementary files

Article information

Article type
Paper
Submitted
10 Nov 2016
Accepted
29 Nov 2016
First published
30 Nov 2016

Org. Biomol. Chem., 2017,15, 426-434

Mechanistic insight into the acid-catalyzed isomerization of biomass-derived polysubstituted pyrrolidines: an experimental and DFT study

G. G. Gerosa, N. Grimblat, R. A. Spanevello, A. G. Suárez and A. M. Sarotti, Org. Biomol. Chem., 2017, 15, 426 DOI: 10.1039/C6OB02457B

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