Sequential [3 + 2] and [4 + 2] cycloadditions for stereoselective synthesis of a novel polyheterocyclic scaffold.

A strategy of combining [3 + 2] cycloaddition and intramolecular Diels-Alder reaction is developed for the synthesis of a novel polycyclic scaffold with skeletal and substitutional diversities. Intermediates generated from stereoselective [3 + 2] cycloaddition of azomethine ylides and maleimides were derivatized for intramolecular Diels-Alder reaction of furan to form highly condensed heterocyclic products as racemic single diastereomers.