One-Step Carbon Homologation of Cyclopentene to Cyclohexene via Tandem Isomerization–Metathesis

Cyclohexene is an important feedstock for the production of nylon precursors and other value-added chemicals, whereas cyclopentene has comparatively limited industrial applications. Therefore, the selective conversion of cyclopentene into cyclohexene represents an attractive strategy for increasing product value while expanding the utility of cyclopentene-rich streams. Herein, we report a one-step carbon homologation strategy for the conversion of cyclopentene to cyclohexene via tandem isomerization–metathesis (ISOMET). Reaction screening identified 5 M and 50 °C as the optimal conditions. Under these conditions, cyclohexene was obtained in 55% yield, corresponding to 73% of the theoretical maximum yield (75%), and the reaction was essentially complete within 12 h. The turnover numbers reached 11,400 and 45,600 for the metathesis and isomerization catalysts, respectively. To demonstrate the broader applicability of this approach, the optimized homologation strategy was applied to a cyclopentene-rich product mixture obtained from polybutadiene (PBD) depolymerization. Homologation substantially shifted the product distribution toward C6 cyclic products, increasing their fraction from 24% to 66%. These results demonstrate that cyclopentene homologation provides an effective route to cyclohexene and other valuable C6 products, enabling the upgrading of depolymerization-derived product streams.