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A Bifunctional β-Isocupreidine Derivative as Catalyst for the Enantioselective Morita-Baylis-Hillman Reaction and a Mechanistic Rationale for Enantioselectivity

Authors :
Mario Orena
Gianluca Martelli
Samuele Rinaldi
Source :
European Journal of Organic Chemistry. 2012:4140-4152
Publication Year :
2012
Publisher :
Wiley, 2012.

Abstract

Starting from β-isocupreidine (β-ICD), a series of difunctional catalysts were synthesized to ascertain their usefulness in the asymmetric Morita–Baylis–Hillman (MBH) reaction. The trichloroacetylcarbamate derivative was found to give the (R)-MBH adducts in excellent optical purities (90–99 % ee) and moderate to good yields (43–83 %), in some cases, better than β-ICD. A number of acrylates were also tested and 2,6-dimethyl-4-nitrophenyl acrylate was identified as a suitable alternative to the popular hexafluoroisopropyl acrylate, with both the β-ICD and trichloroacetylcarbamate derivatives. The mechanism of the rate- and selectivity-determining step was ascertained by means of experimental observations and a computational investigation aimed at clarifying the transition state structures is reported. These studies have clarified the reasons for the effectiveness of these structurally related catalysts in the asymmetric MBH reaction between acrylates and aldehydes.

Details

ISSN :
1434193X
Volume :
2012
Database :
OpenAIRE
Journal :
European Journal of Organic Chemistry
Accession number :
edsair.doi...........6f9fb32226af21b61056467399210097
Full Text :
https://doi.org/10.1002/ejoc.201200405