Studies on the Lewis acid mediated cleavage of α-aminoacetals: synthesis of novel 1,2-aminoethers, and evidence for α-alkoxy aziridinium ion intermediates

Abstract

The nucleophilic cleavage of α-amino acetals induced by TMSOTf can be used to prepare a wide range of substituted 1,2-aminoethers. In particular, organometallic reagents, N-heterocycles, and enamines all react efficiently to give products in good yield. In appropriate cases, good levels of stereocontrol are possible, but this is very dependent on the nature of the nucleophile and the substrate, with diethylzinc proving particularly effective across a range of substrates. The degree of stereocontrol can be used to infer the nature of the reactive intermediates involved in the reaction. With diethylzinc, it is most likely that the reaction proceeds by coordination of the nucleophile to the amino group followed by transfer of an ethyl group to an α-oxocarbenium ion. With non-coordinating nucleophiles, the stereochemical outcome can be rationalised in terms of addition to the possible α-alkoxy aziridinium ion intermediates.