Chiral imines on the wave: reactivity of tert-butyl acrylate and stereoselectivity determination using NMR in liquid crystals
Résumé
In connection with synthetic applications, we have foreseen to study the reactivity of the poorly reactive $tert$-butyl acrylate electrophile with chiral imines of unsymmetrical ketones, using conventional or microwave flash heating under carefully controlled reaction conditions in order to develop a selective and efficient access to the corresponding Michael adducts in which a created stereogenic quaternary carbon center was fully stereocontrolled. Depending on the conditions, either a keto ester or a lactam were obtained. A good correlation was obtained between experiment and theoretical calculations. The stereoselectivity of the process (e>95%) was determined using natural abundance $^{13}$C-{$^1$H} NMR in a chiral polypeptide liquid crystal. The scope of the reaction was screened using a set of electrophilic alkenes giving Michael adducts in good yield and similar high enantiocontrol.
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