Synthesis of heterocyclic enamine-zinc complexes as precursors of stereocontrolled substitution of nitrogen α-position

Abstract

In the presence of ZnCl2, chiral protected amino-ketones and amino-aldehydes gave zinc enamino-complexes. Both enamine and iminium structures of these complexes were observed in 1H and 13C NMR spectra depending on the solvent. Introduction of either an allyl or a hydrogen substituent was performed using allylmagnesium chloride or NaBH4 in excess leading to various heterocycles. With the amino-ketones diastereoselectivity (de = 50) was observed respectively. Homoconiine and coniine precursors were prepared by this strategy.