Theoretical investigation on the mechanism of ferrocenecarboxaldehyde-catalyzed direct β-alkylation of 1-phenylethanol with benzyl alcohol

DFT methods have been used to study the reaction mechanism of 1-phenylethanol with benzyl alcohol catalyzed by ferrocenecarboxaldehyde/NaOH. The structures of intermediates and transition states, and the exchange of electronic density are computed in detail. In general, the catalyzed reaction is consists of three steps: hydride transfer step with the electron transfer, crossing-aldol condensation step, and the reduction step. Hydride transfer is the speed control step with the highest energy barrier (about 32 kcal/mol). Our calculation results are fundamentally coincident with the experimental detections, and manifest the crossing-coupling reaction occurs through a reliable mechanism.

In this paper, we investigated the mechanism of 1-phenylethanol β-alkylation with benzyl alcohol using DFT methods at the M062x level. In the reaction, the ferrocenecarboxaldehyde is the catalyst and p-xylene is chosen as the solvent, which is consistent with the experimental conditions. The calculated results show that the entire catalytic cycle includes three successive steps: (1) hydride transfer; (2) cross-aldol condensation; and (3) reduction. The iron catalyst slips the Cp ring to maintain its 18e stable structure in the reaction process. The present investigation is in good agreement with the experiment results.Figure optionsDownload as PowerPoint slide