Iron-Catalyzed Divergent Tandem Radical Annulation of Aldehydes with Olefins toward Indolines and Dihydropyrans

Iron-catalyzed divergent tandem radical annulations of aldehydes with olefins are reported. The new strategy allows the rapid and efficient construction of various multifunctionlized indolines (R = Ar) and dihydropyrans (R = Me), which are significant skeletons in bioactive natural products and pharmaceuticals. The substituents of tertiary amines play vital roles to facilitate the desired transformation. Mechanistic studies on indoline formation disclose that the homolytic cleavage of the carbonyl C–H bond might be involved in the rate-determining step, while dissociation of the aromatic C–H bond was most likely included in the product-determining step

Iron-Catalyzed Acylation-Oxygenation of Terminal Alkenes for the Synthesis of Dihydrofurans Bearing a Quaternary Carbon

Iron-catalyzed acylation-oxygenation of terminal alkenes is reported. Acyl radicals generated by the oxidation of aldehydes add to terminal alkenes and followed by intramolecular oxygenation give functionalized 2,3-dihydrofuran derivatives bearing a quaternary carbon

Influence of Framework Protons on the Adsorption Sites of the Benzene/HY System

Monte Carlo (MC) simulations were performed to study the influence of framework protons on the adsorption sites of the benzene molecule in HY zeolite with different Si:Al ratios. Eleven types of adsorption sites were observed including five reported sites (H1, H2, U4, U4­(H1), and W) and six newfound sites (W­(2H1), U4­(2H1), H1­(H2), U4­(H1,H1), H1­(H2,H1), and U4­(H1,H1,H1)), which were “supersites” with more than one proton. The stability order of the sites found in the 28Al model can be expressed as U4­(H1,H1,H1) > U4­(H1) > H1­(H2,H1) > W­(2H1) > U4­(H1,H1) > H1­(H2) > H1 > H2 > U4 > U4­(2H1) > W. Increasing number of zeolite protons resulted in an increasing proportion of supersites, which enhanced adsorption energies of sites. For HY zeolite models containing different numbers of protons with the same ratio of H1:H2, the amount of the most stable adsorption sites containing H1 proton increased, while the amount of the most stable adsorption sites containing H2 decreased, with increasing number of protons

Dissolution and Absorption: A Molecular Mechanism of Mesopore Formation in Alkaline Treatment of Zeolite

With the aim to optimize alkaline treatment of zeolites to obtain hierarchical zeolites, dissolution and absorption mechanisms relevant to mesopore formation were investigated at an atomistic scale by density functional calculations. In the dissolution processes, dealumination is energetically more favorable than desilication, though both processes can occur. The dissolved Al species prefer to be absorbed back onto zeolite surfaces whereas the dissolved Si species tend to aggregate in solution. The dissolution process promotes but the absorption process hampers the mesopore formation, laying foundation for understanding the mesoporosity influenced by the variations of zeolite framework and solution

Direct Benzothiophene Formation via Oxygen-Triggered Intermolecular Cyclization of Thiophenols and Alkynes Assisted by Manganese/PhCOOH

An intermolecular oxidative cyclization between thiophenols and alkynes for benzothiophene formation has been established. A variety of multifunctional benzothiophenes are synthesized. In addition, we demonstrated that the obtained benzothiophenes can be used for further transformation to give diverse benzothiophene derivatives efficiently and selectively

Promotion of the Inactive Iron Sulfide to an Efficient Hydrodesulfurization Catalyst

Extensive efforts have been devoted to developing desulfurization catalysts to effectively remove sulfur from fuel. Active phase metals including cobalt, nickel, molybdenum, and tungsten have been extensively used in industry for hydrotreating/hydrodesulfurization catalysts for over 50 years. However, while it is desirable to use inexpensive materials to do the same job, it is a grand challenge. Herein, we report a Fe-based sulfide catalyst that is tuned by zinc with high activity for HDS, which shows an industrial application potential to replace industrial Mo-based catalysts. With an optimal configuration that has a Fe:Zn ratio close to 1:1, the reaction rate constants of the dibenzothiophene (DBT) and 4,6-dimethydibenzothiophene (4,6-DMDBT) HDS are increased by 9.2 and 17.4 times, respectively, in comparison with the sums of those on the monoiron and zinc sulfides. HDS activity for the sterically hindered 4,6-DMDBT on the FeZn sulfide catalyst is even close to that of Co-MoS₂. The experimental results indicate that the addition of Zn greatly modifies the electronic properties of iron sulfide by transferring electrons from Zn to Fe, which tunes the d band center to modulate the adsorption behavior of DBT and 4,6-DMDBT. In combination with theoretical calculations, our experiments show that the addition of Zn dramatically tunes the formation of sulfur vacancies. We propose that the formation of sulfur vacancies is the critical factor for designing highly efficient Fe-based sulfide catalysts. This study provides the design principle of low-cost desulfurization catalysts for industrial refinery applications