Co‐Cluster‐Based Metal–Organic Frameworks as Selective Catalysts for Benzene Tandem Acylation–Nazarov Cyclization to Benzocyclopentanone

Abstract

One-step selective benzene acylation-Nazarov cyclization is an attractive, yet challenging method for the synthesis of the benzocyclopentanone skeleton, which is key intermediate of many natural products. Herein, two metal-cluster-based metal-organic frameworks (MCOFs) {(H O) [Co (pbcd) (μ -OH) ]⋅CH CH OH⋅4 H O} (1; pbcd=9,9'-(propan-1,3-diyl)bis(9H-carbazole-3,6-dicarboxylic acid) and {[Co (mcd) (HCO )(μ -O) (μ -OH) (H O) ]⋅6 H O⋅5 DMF} (2; mcd=9,9'-methylenebis(9H-carbazole-3,6-dicarboxylic acid) were developed to catalyze a tandem Nazarov cyclization reaction of 1,3-dimethoxybenzene with α,β-unsaturated carboxylic acids for the synthesis of cyclopentenone[b]benzenes. MCOFs 1 and 2, which were constructed from tetranuclear Co cluster [Co (μ -OH) ] and hexanuclear Co cluster [Co (HCO )(μ -O)(μ -OH)], respectively, exhibit high catalytic activity arising not only from their suitable channel size and accessible catalytic sites, but also because of their high density of Lewis acidic sites within the frameworks and the synergic activity among Co ions. In contrast, {[Co (pbcd)(bpe)]⋅2 H O⋅2 DMF} (3; bpe=1,2-bis(pyridin-4-yl)ethane) containing binuclear Co and having large pore windows is a highly selective catalyst for obtaining exclusively the acylation products. Easy product separation, simple reaction procedures, and catalyst recycling make the catalyst system attractive. This work highlights the synergistic effect among ions of MCOFs in interacting with substrates in a sequential or cooperative manner to achieve tandem catalysis.

A Highly Sensitive and Recyclable Ln‐MOF Luminescent Sensor for the Efficient Detection of Fe3+ and CrVI Anions

“…All the reagents and solvents were commercially available and used without further purification. The ligand H 4 mcd was synthesized according to the reported experimental procedure . A Bruker Tensor 27 spectrophotometer using dry KBr disks was applied to measure FT‐IR (Fourier transform infrared) spectra in the 4000–400 cm −1 range.…”

Z‐Scheme In2S3/NU‐1000 Heterojunction for Boosting Photo‐Oxidation of Sulfide into Sulfoxide under Ambient Conditions

“…However, there are still some problems need to be addressed before the wide applications of photocatalysts in the transformation of sulfide to sulfoxide. One of the key issues is that, as an efficient photocatalyst for organic transformations, the high porosity nature of the photocatalyst is crucial to affect the performance of a catalytic reaction [10] . The porosity can reduce the kinetic shielding and facilitate the diffusion of molecular reactants and products.…”

Metal–Organic Framework (MOF)‐Based Materials as Heterogeneous Catalysts for C−H Bond Activation

“…The coordinations ites of metal nodes are either coordinatively vacant or coordinate to volatile solventm olecules, such as water,a lcohol, and DMF,w hich can be easily removed/replacedw ithoutd ecomposition of their original framework structures in the single and well-defined environment.U nsaturated metal centers behavel ike Lewis acidic sites to come into contact with different substrate molecules depending on the properties of the metal ions to realize highly efficient CÀHf unctionalization catalysis. [39][40][41][42][43][44][45] The other subgroup is post-metalation on nodes of some chemically and thermally stable MOFs based on non-redox metals, for example, Zr-based MOFs.A tt he nodes of these Zr-MOFs, there are differentt ypes of aqua and hydroxo groups, that is, m 3 -OH, ÀOH 2 ,a nd ÀOH with ab road range of acidities, bridging modes, and densities. These groups behave in the manner of a discrete solid-support-like "ligand" to allow the PSM through chemicalb inding with active species, especially with molecular catalysts or low-valent transition metals,w hich exhibit excellent catalytic activitieso fC ÀHa ctivation.…”

“…The coordination sites of metal nodes are either coordinatively vacant or coordinate to volatile solvent molecules, such as water, alcohol, and DMF, which can be easily removed/replaced without decomposition of their original framework structures in the single and well‐defined environment. Unsaturated metal centers behave like Lewis acidic sites to come into contact with different substrate molecules depending on the properties of the metal ions to realize highly efficient C−H functionalization catalysis . The other subgroup is post‐metalation on nodes of some chemically and thermally stable MOFs based on non‐redox metals, for example, Zr‐based MOFs.…”