Lanthanide(III)-Catalyzed Synthesis of trans-Diaminocyclopentenones from Substituted Furfurals and Secondary Amines via a Domino Ring-Opening/4π-Electrocyclization Pathway.

A strategy toward the synthesis of trans-4,5-diaminocyclopent-2-enones is described. This core motif is embedded in the marine sponge derived alkaloids agelamadin B and nagelamide J. A variety of 2-substituted trans-4,5-diaminocyclopent-2-enones were synthesized in good to quantitative yields using lanthanide(III) catalysis. The products were formed exclusively as the trans-diastereomers via a mechanism in which the C4-C5 bond formation occurs through a 4π-conrotatory electrocyclization. The precursor 3-substituted furfurals can be readily accessed using palladium(0)-catalyzed cross-coupling between 3-bromofurfural and boronic acids, trifluoroborate salts, or alkynes.