A Pd(0) π-Lewis base-initiated cascade transformation of 1,3-enyne-tethered malononitriles is disclosed, proceeding through intramolecular vinylogous addition of the nucleophilicity-enhanced alkyne moiety to a pendent cyano group, cis/trans isomerization, and Suzuki coupling, followed by 6π-aza-electrocyclization and oxidative aromatization. A range of cyclopentabpyridines are constructed straightforwardly, while azafluorenes are obtained instead in the presence of formic acid. Moderate enantioselectivity is also achieved using a chiral sulfinamide-phosphine ligand.
Li et al. (Mon,) studied this question.