Preparation of non-racemic single-stereocentre α-aminonitriles and a study of their fate in Bruylants reactions |
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Authors: | Virginie Beaufort-Droal |
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Institution: | Laboratoire SEESIB (UMR 6504—CNRS), Département de Chimie, Université Blaise Pascal—Clermont-Ferrand II, 24 avenue des Landais, 63177 Aubière cedex, France |
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Abstract: | A number of chiral carboxamide dehydration methods were investigated for the preparation of four representative enantiomerically enriched α-aminonitriles possessing only one stereogenic centre; best results were observed using Burgess' salt (yield up to 87%, er up to 92/8) or the trifluoroacetic anhydride-triethylamine combination (yield up to 98%, er up to 86/14). Two of the aminonitriles thus obtained were subjected to Bruylants reactions with a methyl Grignard reagent to furnish the corresponding tertiary amines; these products, along with any unreacted starting materials, were obtained essentially in racemic form. In accord with the accepted mechanism for this reaction, a magnesium species is implicated in the formation of an iminium, the common intermediate for both chemical transformation and racemization processes. |
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