Enantioselective Synthesis of a New Class of Stable and Functionalized Cyclopentadienes via CuH-Catalysis

Cyclopentadienes (CpHs) are fundamental building blocks across chemistry, yet their inherent acidity and tendency to undergo rapid [1,5]-hydrogen shifts have long limited access to structurally and configurationally stable chiral variants. Overcoming this intrinsic fluxionality remains a major synthetic challenge that limits the potential of CpHs in asymmetric synthesis. Here we present a CuH-catalyzed transformation that converts simple precursors into highly functionalized and enantioenriched CpHs in high yield and with exceptional enantioselectivity. Computations uncover the origins of the observed selectivity and show the reaction mechanism to involve a rare example of nitrile activation in Cu-catalysis. The disclosed new class of CpHs is unexpectedly stable, which was found to be attributed to a conjugated push-pull electronic effect that delineates a new general design principle for taming the intrinsic instability of CpHs.