ChemInform Abstract: An Efficient, High Yielding, and Eco-Friendly Method for the Synthesis of 14-Aryl- or 14-Alkyl-14H-dibenzo[a,j]xanthenes Using Polyvinylsulfonic Acid as a Recyclable Broensted Acid Catalyst.

The silicoaluminophosphate zeotype ECR-40, which has the MEI topology, contains linkages of AlO4 tetrahedra via a common oxygen atom, thereby violating the famous “Löwenstein’s rule”. Due to the proven existence of Al-O-Al linkages in this material, it constitutes an ideal model system to study the acidity and mobility of protons associated with such unusual linkages. In addition, their properties can be directly compared to those of protons associated with more common Si-O-Al linkages, which are also present in ECR-40. In this work, static density functional theory (DFT) calculations including a dispersion correction were employed to study the preferred proton sites as well as the Brønsted acidity of the framework protons, followed by DFT-based ab-initio molecular dynamics (AIMD) to investigate the proton mobility in guest-free and hydrated ECR-40. Initially, two different proton arrangements were compared, one containing both H[O6] protons associated with Al-O-Al linkages and H[O10] protons at Si-O-Al linkages, the other one containing only H[O10] protons. The former model was found to be thermodynamically favoured, as a removal of protons from the Al-O-Al linkages causes a local accumulation of negative charge. Calculations of the deprotonation energy showed a moderately higher Brønsted acidity of the H[O10] protons, at variance with previous empirical explanations, which attributed the exceptional performance of ECR-40 as acid catalyst to the presence of Al‑O‑Al linkages. The AIMD simulations (T = 298 K) delivered no appreciable proton mobility for guest-free ECR-40 and for low levels of hydration (one H2O per framework proton). Under saturation conditions, framework deprotonation occurred, leading to the formation of protonated water clusters in the pores. Pronounced differences between the two types of framework protons were observed: While the H[O10] protons were always removed from the Si-O-Al linkages, the Al-O-Al linkages remained mostly protonated, but deprotonation did occur to a minor extent. The observation of a degree of framework deprotonation of Al-O-Al linkages differs from the findings reported in a recent computational study of hydrated aluminosilicate zeolites with such linkages (Heard et al., Chem. Sci. 2019, 10, 5705), pointing to an influence of the overall framework composition. Further inspection of the AIMD results showed that a coordination of water molecules to framework Al atoms occurred in many cases, especially in the vicinity of the Al-O-Al linkages, sometimes resulting in a pronounced modification of the linkages through additional bridging oxygen atoms. Given the changes in the local structure, it can be expected that such modified linkages are especially prone to break upon dehydration. Thus, in addition to elucidating the deprotonation behaviour of protons associated with different types of linkages, the calculations also provide insights into possible reasons for the instability of Al-O-Al linkages, clarifying why Löwenstein’s rule is mostly obeyed in materials that are formed via a hydrothermal route.

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Computationally-Guided Investigation of Dual Amine/pi Lewis Acid Catalysts for Direct Additions of Aldehydes and Ketones to Unactivated Alkenes and Alkynes

10.26434/chemrxiv.7538114.v2 ◽

2020 ◽

Author(s):

Eric Greve ◽

Jacob D. Porter ◽

Chris Dockendorff

Keyword(s):

Lewis Acid ◽

Density Functional ◽

Acid Catalyst ◽

Metal Catalyst ◽

Catalyst Poisoning ◽

Lewis Acid Catalysts ◽

Metal Ligands ◽

Aldehydes And Ketones ◽

Lewis Acid Catalyst ◽

Catalyst Systems

Dual amine/pi Lewis acid catalyst systems have been reported for intramolecular direct additions of aldehydes/ketones to unactivated alkynes and occasionally alkenes, but related intermolecular reactions are rare and not presently of significant synthetic utility, likely due to undesired coordination of enamine intermediates to the metal catalyst. We reasoned that bulky metal ligands and bulky amine catalysts could minimize catalyst poisoning and could facilitate certain examples of direct intermolecular additions of aldehyde/ketones to alkenes/alkynes. Density Functional Theory (DFT) calculations were performed that suggested that PyBOX-Pt(II) catalysts for alkene/alkyne activation could be combined with MacMillan’s imidazolidinone organocatalyst for aldehyde/ketone activation to facilitate desirable C-C bond formations, and certain reactions were calculated to be more exergonic than catalyst poisoning pathways. As calculated, preformed enamines generated from the MacMillan imidazolidinone did not displace ethylene from a biscationic (t-Bu)PyBOX-Pt2+complex, but neither were the desired C-C bond formations observed under several different conditions.

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Computationally-Guided Investigation of Dual Amine/pi Lewis Acid Catalysts for Direct Additions of Aldehydes and Ketones to Unactivated Alkenes and Alkynes

10.26434/chemrxiv.7538114 ◽

2020 ◽

Author(s):

Eric Greve ◽

Jacob D. Porter ◽

Chris Dockendorff

Keyword(s):

Lewis Acid ◽

Density Functional ◽

Acid Catalyst ◽

Metal Catalyst ◽

Catalyst Poisoning ◽

Lewis Acid Catalysts ◽

Metal Ligands ◽

Aldehydes And Ketones ◽

Lewis Acid Catalyst ◽

Catalyst Systems

Dual amine/pi Lewis acid catalyst systems have been reported for intramolecular direct additions of aldehydes/ketones to unactivated alkynes and occasionally alkenes, but related intermolecular reactions are rare and not presently of significant synthetic utility, likely due to undesired coordination of enamine intermediates to the metal catalyst. We reasoned that bulky metal ligands and bulky amine catalysts could minimize catalyst poisoning and could facilitate certain examples of direct intermolecular additions of aldehyde/ketones to alkenes/alkynes. Density Functional Theory (DFT) calculations were performed that suggested that PyBOX-Pt(II) catalysts for alkene/alkyne activation could be combined with MacMillan’s imidazolidinone organocatalyst for aldehyde/ketone activation to facilitate desirable C-C bond formations, and certain reactions were calculated to be more exergonic than catalyst poisoning pathways. As calculated, preformed enamines generated from the MacMillan imidazolidinone did not displace ethylene from a biscationic (t-Bu)PyBOX-Pt2+complex, but neither were the desired C-C bond formations observed under several different conditions.

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Preparation and Characterization of WO3/ZrO2 Solid Acid Catalyst with Hierarchically Porous Structure

CHINESE JOURNAL OF CATALYSIS (CHINESE VERSION) ◽

10.3724/sp.j.1088.2011.01203 ◽

2011 ◽

Vol 32 (4) ◽

pp. 647-651

Author(s):

Chongcheng CHEN ◽

Hangrong CHEN ◽

Jianchang YU ◽

Zhengqing YE ◽

Jianlin SHI

Keyword(s):

Porous Structure ◽

Solid Acid ◽

Solid Acid Catalyst ◽

Acid Catalyst ◽

Hierarchically Porous ◽

Hierarchically Porous Structure

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SO3H-functionalized Zeolite-Y as an Efficient Nanocatalyst for the Synthesis of Nbenzimidazole- 2-aryl-4-thiazolidinones and tri-substituted Imidazoles

Current Organic Synthesis ◽

10.2174/1570179417666200115170019 ◽

2020 ◽

Vol 17 (2) ◽

pp. 117-130 ◽

Cited By ~ 1

Author(s):

Mehdi Kalhor ◽

Zohre Zarnegar ◽

Zahra Seyedzade ◽

Soodabeh Banibairami

Keyword(s):

Zeolite Y ◽

Internal Standard ◽

Acid Catalyst ◽

Aromatic Aldehydes ◽

Reaction Rates ◽

Ambient Conditions ◽

Catalytic Method ◽

Efficient Catalyst ◽

Bet Analysis ◽

Ft Ir

Background: SO3H-functionalized zeolite-Y was prepared and used as a catalyst for the synthesis of 2-aryl-N-benzimidazole-4-thiazolidinones and tri-substituted imidazoles at ambient conditions. Objective: The goals of this catalytic method include excellent yields and high purity, inexpensive procedure and ease of product isolation, the use of nontoxic and heterogeneous acid catalyst, shorter reaction times and milder conditions. Materials and Methods: NMR spectra were recorded on Brucker spectrophotometer using Me4Si as internal standard. Mass spectra were recorded on an Agilent Technology 5975C VL MSD with tripe-axis detector. FTIR spectra were obtained with KBr disc on a galaxy series FT-IR 5000 spectrometer. The surface morphology of nanostructures was analyzed by FE-SEM (EVO LS 10, Zeiss, Carl Zeiss, Germany). BET analysis were measured at 196 °C by a Japan Belsorb II system after the samples were vacuum dried at 150°C overnight. Results: The NSZ was characterized by FT-IR, FESEM, EDX, XRF, and BET. The catalytic activity of NSZ was investigated for synthesis of 1,3-tiazolidin-4-ones in H2O/Acetone at room temperature. Moreover, NSZ was used for synthesis of tri-substituted imidazoles at 60 °C via solvent-free condensation. Different kinds of aromatic aldehydes were converted to the corresponding of products with good to excellent yields. Conclusion: Sulfonated zeolite-Y was as an efficient catalyst for the preparation of N-benzimidazole-2-aryl-1,3- thiazolidin-4-ones and 2,4,5-triaryl-1H-imidazoles. High reaction rates, elimination toxic solvent, simple experimental procedure and reusability of the catalyst are the important features of this protocol.

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