Azomethine ylide cycloaddition of 1,3-dienyl esters: highly regio- and diastereoselective synthesis of functionalized pyrrolidinochromenes

Abstract

An efficient protocol for the synthesis of tricyclic pyrrolidinochromenes has been developed via an intramolecular 1,3-dipolar cycloaddition of azomethine ylides generated in situ from 1,3-dienyl ester tethered O-hydroxyarylaldehyde and glycine esters. The reaction is highly regio- and diastereoselective in nature and provided the potentially bioactive pyrrolidine fused tricyclic cycloadducts in excellent yields with wide substrate scope. Interestingly this reaction constructs two rings and four contiguous stereogenic centers in which one of them is an all carbon quaternary center in a unique fashion.