Stereocontrolled Construction of Spirooxindole-Containing 5,6,7,8-Tetrahydropyrrolo[1,2- a]pyridine via Michael/Friedel-Crafts Domino Reaction Promoted by Secondary Amine-Squaramide

Org Lett. 2024 Mar 22;26(11):2152-2157. doi: 10.1021/acs.orglett.4c00073. Epub 2024 Mar 8.

Abstract

An asymmetric Michael/Friedel-Crafts cascade reaction with Morita-Baylis-Hillman (MBH) nitroallylic esters and 3-pyrrolyloxindoles has been developed for the stereoselective construction of spirooxindole-containing tetrahydroindolizines. A range of tetracyclic scaffolds possessing three consecutive chiral centers, including an all-carbon quaternary stereocenter, were generated in 53-85% isolated yields with high diastereoselectivities and enantiopurities (≥3:1 dr, 50-98% ee). A newly synthesized bifunctional secondary amine/squaramide organocatalyst was demonstrated to exhibit better stereochemical control than their tertiary analogues.