Catalyst-free Tandem 1,3-Dipolar Cycloaddition/Aldol Condensation: Diastereoselective Construction of the Azatetraquinane Skeleton

The one-pot regioselective and diastereoselective method for the synthesis of 5-(het)­aroyl-7-(het)­arylhexahydrobenzo­[4,5]­pentaleno­[1,6a-b]­(thia)­pyrrolizine-6,12-diones from accessible 1,5-di­(het)­arylpent-4-ene-1,3-diones or curcuminoids in 38–98% yield was developed. This reaction proceeds as a sequence of 1,3-dipolar cycloaddition of azomethine ylide generated in situ from ninhydrin and (thia)­proline at the CC bond of corresponding enedione, followed by spontaneous intramolecular aldol condensation and leads to the formation of an azatetraquinane scaffold.