We report a method for the synthesis of 2-substituted benzoxazoles from tertiary amides and 2-aminophenols in the presence of triflic anhydride (Tf2O) and 2-Fluoropyridine (2-F-Pyr). The cascade reaction involves the activation of the amide carbonyl group by Tf2O, nucleophilic addition, intramolecular cyclization, and elimination. Furthermore, we explore the scope of this method by varying both the amide and 2-aminophenol substrates, highlighting its versatility in the synthesis of a wide range of functionalized benzoxazole derivatives.
The hydroesterification of olefins provides a highly efficient way to produce high value-added ester products from simple and abundant olefin feedstocks. In this work, DFT calculation was performed to investigate the detailed reaction mechanism of propene hydroesterification over Rh(II)/Silicalite-2 catalysts. Three possible mechanistic pathways were systematically explored and compared in terms of their adsorption configurations, reaction energies, and transition-state barriers. Among them, the Carbonylation-First pathway exhibited the most favorable energy profile with the lowest overall kinetic barriers, indicating it to be the most likely way for ester formation. A comparison of methyl butyrate and methyl isobutyrate formation revealed that the linear product is energetically more favorable, particularly along the Carbonylation-First pathway. Moreover, the Rh(II) center demonstrates a different catalytic effect over conventional Rh(I) species by significantly lowering the energy barrier for CO insertion, a key step in both hydroformylation and hydroesterification. These findings provide fundamental insight into the role of Rh(II)/zeolite systems in carbonylation reactions and offer theoretical guidance for the design of catalysts.
Incorporating comonomers in propylene polymerization plays a critical role in tuning the physical and chemical properties of the resulting polymers. In this study, the impact of three developed comonomers on propylene polymerization over the triethylaluminum-treated TiCl3 catalyst was investigated in detail by DFT. The results indicate that these comonomers remain highly stable under actual catalytic conditions, with their ions or functional groups showing a low propensity for detachment, which would otherwise poison the catalyst or disrupt the polymerization process. However, the three comonomers on the surface with a strong adsorption capacity may compete with propylene for adsorption, which will affect the polymerization. Among them, Vinyltrimethoxysilane, which exhibits the strongest adsorption ability, tends to form bonds with the ethyl on the catalyst surface, leading to catalyst poisoning and inhibiting the reaction. In contrast, 5-hexenyl methyldichlorosilane demonstrates relatively higher activity due to its balanced properties. The order of reactivity in the polymerization reaction: 5-hexenyl methyldichlorosilane > 5-hexenyldichlorophosphonane > vinyltrimethoxysilane. This work provides fundamental mechanistic insights into how functional comonomers interact with catalytic active sites through adsorption, competitive reactions, and insertion processes. Additional free energy analysis at 333 K confirms that these mechanistic trends remain unchanged under realistic reaction conditions. Rather than directly simulating industrial catalysts, the present study focuses on a model TiCl3 system to elucidate intrinsic structure-reactivity relationships. These findings contribute to a deeper understanding of comonomer effects in olefin polymerization at the molecular level.