Michael-type addition of phthalimide salts to chiral α,β-unsaturated imides

Article abstract of DOI:10.1016/S0040-4039(00)73317-X

The synthesis of (R)-(-)-3-aminobutanoic acid starting from chiral α,β- unsaturated imide 1b is described, by means of the nucleophilic attack of several phthalimido derivatives in the presence of a Lewis acid. The reaction was studied in some details and chloromagnesium phthalimide afforded the better results with 95:5 diastereomeric ratio and 90% yield. Furthermore the resulting enolate was trapped performing the reaction in the presence of benzenesulfonyl bromide and the 2-bromo-3-phthalimido derivative 4 was obtained in good yield and high diastereoselectivity and successively transformed into the corresponding 2-azido-3-phthalimido derivative 6 by displacement of the bromide with sodium azide.