En Route Investigation of Reaction Conditions’ Influence on Cross‐Metathesis Yields Employing Grubbs 2^nd Generation–<i>p</i>‐Cresol Catalyst Derivative – Part 1

Abstract

Abstract A study investigated the ideal p ‐cresol to Grubbs second‐generation catalyst ( GII ) ratio for maximizing selectivity in cross‐metathesis reactions. Adding p ‐cresol to GII enhances selectivity for cross‐metathesis over self‐metathesis, with 100 equivalents of p ‐cresol ensuring optimal catalyst performance. The study focused on the cross‐metathesis of 2‐ethyl hexyl acrylate and trans ‐anethole, varying trans ‐anethole mole fractions from approximately 0.09 to 0.91. Using 1 H NMR spectroscopy, the reaction progress was monitored at 25 °C and 35 °C in CD 2 Cl 2 solvent over 722 minutes, maintaining a constant p ‐cresol/ GII ratio (100 : 1, X 1 =0.33). The reaction setup followed previous protocols with slight adjustments for time‐trace analysis. Results revealed an induction period at both temperatures, significantly shorter at 35 °C (4 minutes vs. 40 minutes at 25 °C). The elevated temperature notably increased the selectivity of the p ‐cresol/ GII catalyst. Reaction kinetics showed the cross‐metathesis rate with the modified catalyst was approximately 1.5 times faster than self‐metathesis, with k ’ obs values of 0.0575 min −1 (25 °C) and 0.68 min −1 (35 °C) for cross‐metathesis compared to 0.033 min −1 and 0.41 min −1 for self‐metathesis, respectively.