Facile construction of 1,2,6,7,12,12b-hexahydroindolo[2,3-a]quinolizines via one-pot three-component reactions of tryptamines, propiolate, and α,β-unsaturated aromatic aldehydes or ketones

In the presence of anhydrous ZnCl2 the one-pot three-component reaction of tryptamines, propiolates, and α,β-unsaturated aldehydes as well as arylideneacetones afforded the functionalized 1,2,6,7,12,12b-hexahydroindolo[2,3-a]quinolizines in moderate to high yields and with high diastereoselectivity. The reaction mechanism involved the sequential Michael addition and Pictet–Spengler reactions of β-enamino ester generated in situ.