Mild lanthanide(III) catalyzed formation of 4,5-diaminocyclopent-2-enones from 2-furaldehyde and secondary amines: a domino condensation/ring-opening/electrocyclization process

Lewis acid catalyzed reaction of 2-furaldehyde and secondary amines results in the formation of 4,5-diaminocyclopent-2enones exclusively as the trans diastereomers: computational studies support the stereochemistry of the adducts as arising from a thermal conrotatory pi 4a electrocyclization of an initial ring-opened intermediate (a deprotonated Stenhouse salt).