What question did this study set out to answer?

The aim is to develop a new cascade reaction to construct cyclopenta[b]pyridine frameworks from enyne-tethered malononitriles.

February 19, 2026

Construction of Cyclopenta b pyridine Frameworks via Pd(0) π-Lewis Base-Initiated Cascade Reaction of Enyne-Tethered Malononitriles

Key Points

The aim is to develop a new cascade reaction to construct cyclopenta[b]pyridine frameworks from enyne-tethered malononitriles.
Utilized a Pd(0) π-Lewis base-initiated transformation
Conducted intramolecular vinylogous addition of alkyne to cyano group
Performed Suzuki coupling and oxidative aromatization processes
Explored enantioselectivity using chiral ligands
A variety of cyclopenta[b]pyridines were straightforwardly constructed
Azafluorenes were produced in the presence of formic acid instead
Moderate enantioselectivity was achieved with a chiral ligand

Abstract

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.

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