Organocatalysts for the asymmetric reduction of aromatic ketimines with trichlorosilane

QD Chemistry

MacDougall, Kenneth N. ; Kocovsky, Pavel

University:University of Glasgow

Department:School of Chemistry

关键词: organocatalysis, reduction, ketimines, trichlorosilane, synthesis;   

Others  :  http://theses.gla.ac.uk/123/1/2007MacDougall1PhD.pdf

来源: University of Glasgow

【 摘 要 】

Asymmetric reduction of N-aryl ketimines 189a j, 212, and 213 with trichlorosilane can be catalyzed by new N-methyl L-amino acid-derived Lewis-basic organocatalysts, such as bisamide 197c (10 mol%), in toluene at room temperature with high enantioselectivity (≤92% ee). The structure-reactivity investigation shows that the product configuration is controlled by the nature of the side chain of the catalyst scaffold (e.g., i Pr vs Me, as in 197c and 208c), so that catalysts of the same absolute configuration may induce the formation of the opposite enantiomers of the product. Arene-arene interactions between the catalyst and the incoming imine appear to be the prerequisite for asymmetric induction. This metal-free, organocatalytic protocol is competitive with the traditional, metal-catalyzed methodology.