Enantioselective Synthesis of 5,6-Dihydroindolizines by N-Heterocyclic Carbene (NHC)-Catalyzed Core-Structure-Inspired Strategy of Azolium–Enolate Cascade
Arghya Ghosh, Sayan Shee, Shilpa Barik, Rajesh G. Gonnade, Akkattu T. Biju
Abstract
The core-structure motivated design has allowed the enantioselective synthesis of 5,6-dihydroindolizines via N-heterocyclic carbene (NHC) catalysis. The NHC-catalyzed reaction of α,β-unsaturated aldehydes with the suitably substituted pyrrole derivatives proceed via the initial generation of α,β-unsaturated acylazoliums from enals, and enolates from pyrroles and the reaction culminated in an efficient cascade process involving the Michael-aldol-lactonization-decarboxylation sequence to afford the products in reasonable yields and high selectivities. The method is further extended to the construction of spirocyclic 5,6-dihydroindolizines.
Topics & Concepts
Enantioselective synthesisCarbeneChemistryCatalysisAldol reactionDecarboxylationCascadeCombinatorial chemistryPyrroleCascade reactionStereochemistryOrganic chemistryChromatographyN-Heterocyclic Carbenes in Organic and Inorganic ChemistryCyclopropane Reaction MechanismsSynthesis and Reactivity of Heterocycles