Temperature-Dependent Divergent Cyclopentadiene Synthesis through Cobalt-Catalyzed C–C Activation of Cyclopropenes

Abstract

We report a temperature-dependent divergent approach to synthesize multisubstituted cyclopentadienes through cobalt-catalyzed carbon−carbon (C−C) bond activation of cyclopropenes and ring expansion with internal alkynes. By employing different heating procedures, two cyclopentadiene substitution isomers were efficiently and selectively constructed. This reaction does not require preactivation of the metal catalyst or additional reducing reagents. Preliminary mechanistic investigations suggest that the key steps are oxidative addition of the cyclopropene to cobalt catalyst, followed by alkyne insertion and 1,5-ester shift.

Cobalt-Catalyzed (3 + 2) Cycloaddition of Cyclopropene-Tethered Alkynes: Versatile Access to Bicyclic Cyclopentadienyl Systems and Their CpM Complexes

“…This is likely due to their high propensity to generate carbene intermediates, which tend to evolve through cyclopropanations and C–H insertions, among other pathways . Indeed, metal-catalyzed (3 + n ) annulations of cyclopropenes are limited to a handful of processes, most of them promoted by precious metals like Rh, Pd, or Ru. , …”