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Electrosynthesis of Benzothiophenes with symmetrical 2-Alkenylaryl Disulfides
Get PDFDepartment of ChemistryBenzothiophenes are a significant class of heterocyclic compounds due to their wide range of biological applications. It is used as the core structure of various biological molecules. For this reason, the synthesis of this structure has attracted a lot of attention in recent years.
These methods can be broadly classified into two categories(a) Arene with an ortho-alkynyl or alkenyl group activated by reagents produces benzothiophenes through intramolecular cyclization. (b) Functionalized arene and alkyne react with each other to provide benzothiophenes through intermolecular reaction under a transition metal catalysis or other suitable conditions. However, regardless of (a) or (b), most methods require additional additives such as metal catalysts or oxidants that produce unwanted chemical wastes. Recently, an environmentally friendly electrochemical method to solve this problem has been widely developed.
Here, we report a novels synthetic method of benzothiophenes through electrosynthesis in the absence of oxidants and transition metals. Electrolysis of symmetrical 2-alkenylaryl disulfides under undivided cell leads to the formation of corresponding benzothiophenes in good to moderate yields. Unlike previous methods, which typically require the use of transition metal catalysts or chemical oxidants, our method provides a green approach to a useful benzothiophenes.ope
ESSAYS ON THE ROLE OF DIVERSIFICATION IN R&D INVESTMENT
No full textSchool of Business Administration (Management Engineering)clos
Explainable deep learning-based characterization and forecasting of tropical cyclones through the synergistic fusion of satellite observations and numerical model data
No full textDepartment of Urban and Environmental Engineering (Environmental Science and Engineering)clos
Geometrical designs and 3D printing of Cu2Se-based thermoelectric materials and devices
No full textDepartment of Materials Science and Engineeringclos
Highly efficient H2 production process by simultaneous H2 production and CO2 capture: Process simulation and techno-economic analysis
No full textSchool of Energy and Chemical Engineering (Chemical Engineering)Since the Industrial Revolution, ongoing CO2 emissions have caused an environmental issue, global warming. The environment of Earth has been influenced by the climate crisis, which has resulted in a rise in sea levels and frequent natural catastrophes, such as floods and drought. Worldwide nations agreed to address the climate crisis represented by ???Paris Agreement???, aiming to restrict the global average temperature rise below 2 ???, preferably 1.5 ???. In this situation, the renewable energy generated by natural resources such as solar, wind, and so on, is used to replace the carbon-based energy paradigm and achieve the Net Zero. Hence, the renewable energy capacity has grown rapidly as time passed. To store renewable energy, H2 is one of the attractive options in terms of clean production and combustion, durability, and utilization. In addition, H2 is a major component in the refining industry and NH3 production, resulting in a rise in demand for H2. However, most of the H2 is produced using a steam methane reforming process, which emits CO2 due to its low production cost. The H2 should be produced by water electrolysis using renewable energy to achieve carbon neutrality and for a sustainable energy society in the future. Here, a highly efficient H2 production system was proposed as a bridge between current steam methane reforming and the upcoming water electrolysis technology to produce H2. The H2 selective membrane and CO2 adsorbent are used in the proposed method by removing the product (i.e. H2 and CO2) from the reaction site and resulting in a positive equilibrium shift according to Le Chatelier???s Principle. Therefore, process simulation and techno-economic analysis were carried out to evaluate the proposed approach and provide technical and economic insights. For the process simulation, the reactor scale, lab scale, and industrial scale of H2 production were addressed, and a techno-economic analysis included itemized cost estimation, sensitivity analysis, feasibility analysis, and uncertainty analysis.
Based on the reactor scale process design, the effect of sweep gas direction was investigated by a 1D numerical analysis model. And it was revealed that counter-current flow could enhance the H2 permeation amount compared to the co-current flow based on the partial pressure difference. The impact of the employment of an H2 selective membrane and CO2 adsorbent was verified by showing the highest H2 production rate and the lowest CO2 emissions from the sorption-enhanced membrane reactor, which uses the membrane and adsorbent together.
Based on the lab-scale process design, the thermodynamic performance of the conventional reactor, membrane reactor, and sorption-enhanced membrane reactor, was compared in terms of H2 production, CO2 emission, and CH4 conversion. The sorption-enhanced membrane reactor presented the best performance among the three reactorshowever, the lowest levelized cost of H2 was observed for the membrane reactor due to low equipment cost. It was revealed that the levelized cost of H2 of three reactors was still challenging to reach to the one from the current method even though variation of natural gas price and CO2 tax credit was considered.
Based on the industrial scale process design, the process performance and economic feasibility were investigated depending on operating temperature. The amount of H2 production increased and levelized cost of H2 decreased according to the increase in the operating temperature. The levelized cost of H2 of $ 2.27 kgH2-1 was obtained at 700 ??? and the natural gas price was figured out as the critical factor to the levelized cost of H2. In addition, it was unveiled that the positive net present value was observed when the operating temperature was above 600 ??? and the net present value was greatly affected by H2 selling price, which was directly related to the profit.clos
Highly stretchable and tough magnetic-responsive composites with a wide range of modulus tunability for multifunctional soft robots
No full textDepartment of Mechanical EngineeringWe propose two types of multifunctional soft bodies with highly stretchable and tough dual-responsive materials capable of achieving a wide range of variable stiffness values. The primary focus of this dissertation is the wide stiffness variation and rapid thermo-/magneto-responsiveness of highly resilient magnetic composites. Because the proposed highly stretchable and resilient magneto-responsive material allows for large conformational changes when subjected to heat stimuli based on a one-way shape memory effect, it exhibits an excellent shape recovery effect and generates high-power contractile strength.clos
Hypoxia alters the transcriptomic and epigenetic landscape of TNF-?? response in human macrophages
No full textDepartment of Biological Sciencesclos
Meta-Learned Versatile Representations across Heterogeneous Clients
No full textGraduate School of Artificial Intelligenceclos
Nonlinear Fokker-Planck collision operator in Rosenbluth form for gyrokinetic simulations using discontinuous Galerkin method
Get PDFDepartment of Nuclear EngineeringA gyroaveraged nonlinear collision operator is formulated based on the Fokker-Planck operator in the Rosenbluth-MacDonald-Judd (RMJ) potential form and implemented for the gyrokinetic simulations with the discontinuous Galerkin scheme. The divergence structure of the original RMJ form is carefully preserved throughout the formulation to guarantee the density conservation while neglecting the finite Larmor radius effect. The B-spline finite element method is used to calculate the Rosenbluth potentials for the nonlinear collision operator. In addition to the nonlinear collision operator, linear and Dougherty collision models are also implemented to assess the benefits and drawbacks of each model. For the conservation of the parallel momentum and energy, we adopt a simple advection-diffusion model which numerically enforces the conservation of physical quantities. From bump-on-tail relaxation tests, the monotonically increasing entropy in time and conservation properties are demonstrated for the developed collision operator. Also, a few theoretical predictions for the neoclassical physics such as the neoclassical heat flux, poloidal flow and collisional damping of zonal flow are successfully reproduced by numerical simulations.ope
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Get PDFDepartment of ChemistryHeterocycles are highly valuable scaffolds for many useful organic compounds and are frequently found in complex natural products and pharmaceuticals. Their usefulness and extraordinary biological activities drawn a lot of interest in the synthetic community and led to the development of numerous synthetic methodologies. Despite the progress, conventional methods heavily rely on the use of metal catalysts and chemical oxidants that generate unwanted wastes. In this regard, we developed a simple and green strategy for the synthesis of valuable heterocycles with readily available arylalkene substrates.
In chapter 1, previously reported strategies for the synthesis of heterocycles including phthalide, isochroman-1-one, benzofuran, isoindolin-1-one, indole, and benzothiophene, will be described. These methods include transition metal catalysis, visible-light mediated reactions, and electrocatalysis.
In chapter 2, the synthesis of phthalide, isochroman-1-one from 2-alkenylbenzoic acid and isoindolin-1-one from 2-alkenybenzamide under oxidant- and metal-free electrolysis are described. Sequential cathodic reduction and anodic oxidation of 2-alkenylbenzoic acid generate a reactive radical intermediate which either goes through 5-exo or 6-endo cyclizations depending on the reaction conditions. Meanwhile, 2-alkenylbenzamide was prone to oxidation, forming a radical cation intermediate via anodic oxidation, which cyclizes to isoindolin-1-one.
In chapter 3, the synthesis of benzofuran, indole, and benzothiophene from 2-alkenylphenol, 2-alkenylaniline, and 2-alkenylaryl disulfide under oxidant- and metal-free electrolysis are described. These arylalkene substrates were all prone to oxidation which can generate radical cation intermediates and go through spontaneous cyclizations to furnish corresponding heteroarene products. In the case of 2-alkenylphenol, a radical cation generated from anodic oxidation will be trapped by the tosylate anion, which aids the formation of the benzofuran product.ope