scholarly journals Photoinduced Regioselective Olefination of Arenes at Proximal and Distal Sites

2020 ◽  
Author(s):  
Argha Saha ◽  
Srimanta Guin ◽  
Wajid Ali ◽  
Trisha Bhattacharya ◽  
Sheuli Sasmal ◽  
...  
Keyword(s):  
Catalytic System ◽  
Thermal Energy ◽  
Late Stage ◽  
Traditional Approach ◽  
Theoretical Calculations ◽  
Kinetic Studies ◽  
Multiple Site ◽  
Chiral Molecules ◽  
Silver Salts ◽  
Simultaneous Control

The Fujiwara-Moritani reaction has had a profound contribution in the emergence of contemporary C−H activation protocols. Despite the applicability of the traditional approach in different fields, the associated reactivity and regioselectivity issues had rendered it redundant. The revival of this exemplary reaction requires the development of a mechanistic paradigm that would have simultaneous control on both the reactivity and regioselectivity. Often high thermal energy required to promote olefination leads to multiple site functionalization. To this aim we established a photoredox catalytic system constituting a merger of palladium/organo-photocatalyst that forges oxidative olefination in an explicit regioselective fashion of diverse arenes and heteroarenes. Visible light plays a significant role in executing ‘regio-resolved’ Fuijiwara-Moritani reaction without the requirement of silver salts and thermal energy. The catalytic system is also amenable towards proximal and distal olefination aided by respective directing groups (DGs), which entails the versatility of the protocol in engaging the entire spectrum of C(sp<sup>2</sup>)−H olefination. Furthermore, streamlining the synthesis of natural products, chiral molecules, drugs and diversification through late-stage functionalization’s underscore the importance of this sustainable protocol. The photoinduced attainment of this regioselective transformation is mechanistically established through control reactions, kinetic studies and theoretical calculations.

scholarly journals Photoinduced Regioselective Olefination of Arenes at Proximal and Distal Sites

2020 ◽  
Author(s):  
Argha Saha ◽  
Srimanta Guin ◽  
Wajid Ali ◽  
Trisha Bhattacharya ◽  
Sheuli Sasmal ◽  
...  
Keyword(s):  
Catalytic System ◽  
Thermal Energy ◽  
Late Stage ◽  
Traditional Approach ◽  
Theoretical Calculations ◽  
Kinetic Studies ◽  
Multiple Site ◽  
Chiral Molecules ◽  
Silver Salts ◽  
Simultaneous Control

The Fujiwara-Moritani reaction has had a profound contribution in the emergence of contemporary C−H activation protocols. Despite the applicability of the traditional approach in different fields, the associated reactivity and regioselectivity issues had rendered it redundant. The revival of this exemplary reaction requires the development of a mechanistic paradigm that would have simultaneous control on both the reactivity and regioselectivity. Often high thermal energy required to promote olefination leads to multiple site functionalization. To this aim we established a photoredox catalytic system constituting a merger of palladium/organo-photocatalyst that forges oxidative olefination in an explicit regioselective fashion of diverse arenes and heteroarenes. Visible light plays a significant role in executing ‘regio-resolved’ Fuijiwara-Moritani reaction without the requirement of silver salts and thermal energy. The catalytic system is also amenable towards proximal and distal olefination aided by respective directing groups (DGs), which entails the versatility of the protocol in engaging the entire spectrum of C(sp<sup>2</sup>)−H olefination. Furthermore, streamlining the synthesis of natural products, chiral molecules, drugs and diversification through late-stage functionalization’s underscore the importance of this sustainable protocol. The photoinduced attainment of this regioselective transformation is mechanistically established through control reactions, kinetic studies and theoretical calculations.

scholarly journals Photoinduced regioselective olefination of arenes at proximal and distal sites

2020 ◽  
Author(s):  
Debabrata Maiti ◽  
Argha Saha ◽  
Srimanta Guin ◽  
Wajid Ali ◽  
Trisha Bhattacharya ◽  
...  
Keyword(s):  
Natural Products ◽  
Thermal Energy ◽  
Late Stage ◽  
Traditional Approach ◽  
Theoretical Calculations ◽  
Kinetic Studies ◽  
Multiple Site ◽  
Chiral Molecules ◽  
Silver Salts ◽  
Simultaneous Control

Abstract The Fujiwara-Moritani reaction has had a profound contribution in the emergence of contemporary C-H activation protocols. Despite the applicability of the traditional approach in different fields, the associated reactivity and regioselectivity issues had rendered it redundant. The revival of this exemplary reaction requires the development of a mechanistic paradigm that would have simultaneous control on both the reactivity and regioselectivity. Often high thermal energy required to promote olefination leads to multiple site functionalization. To this aim we established a photoredoxcatalytic system constituting a merger of palladium/organo-photocatalyst that forges oxidative olefination in an explicit regioselective fashion of diverse arenes and heteroarenes. Visible light plays a significant role in executing ‘regio-resolved’ Fuijiwara-Moritani reaction without the requirement of silver salts and thermal energy. The catalytic system is also amenable towards proximal and distal olefination aided by respective directing groups (DGs), which entails the versatility of the protocol in engaging the entire spectrum of C(sp2)-H olefination. Furthermore, streamlining the synthesis of natural products, chiral molecules, drugs and diversification through late-stage functionalizations underscore the importance of this sustainable protocol. The photoinduced attainment of this regioselective transformation is mechanistically established through control reactions, kinetic studies and theoretical calculations.

scholarly journals Design Considerations for Borehole Thermal Energy Storage (BTES): A Review with Emphasis on Convective Heat Transfer

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-26 ◽  
Author(s):  
Helge Skarphagen ◽  
David Banks ◽  
Bjørn S. Frengstad ◽  
Harald Gether
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Theoretical Calculations ◽  
High Surface ◽  
High Surface Area ◽  
Volume Ratio ◽  
Thermal Recovery ◽  
Conductive Heat ◽  
Geological Environment

Borehole thermal energy storage (BTES) exploits the high volumetric heat capacity of rock-forming minerals and pore water to store large quantities of heat (or cold) on a seasonal basis in the geological environment. The BTES is a volume of rock or sediment accessed via an array of borehole heat exchangers (BHE). Even well-designed BTES arrays will lose a significant quantity of heat to the adjacent and subjacent rocks/sediments and to the surface; both theoretical calculations and empirical observations suggest that seasonal thermal recovery factors in excess of 50% are difficult to obtain. Storage efficiency may be dramatically reduced in cases where (i) natural groundwater advection through the BTES removes stored heat, (ii) extensive free convection cells (thermosiphons) are allowed to form, and (iii) poor BTES design results in a high surface area/volume ratio of the array shape, allowing high conductive heat losses. The most efficient array shape will typically be a cylinder with similar dimensions of diameter and depth, preferably with an insulated top surface. Despite the potential for moderate thermal recovery, the sheer volume of thermal storage that the natural geological environment offers can still make BTES a very attractive strategy for seasonal thermal energy storage within a “smart” district heat network, especially when coupled with more efficient surficial engineered dynamic thermal energy stores (DTES).

MOLECULAR THEORETICAL CALCULATIONS ON TEMPERATURE DEPENDENCE OF THE PITCH OF CHOLESTERIC LIQUID CRYSTALS

2002 ◽  
Vol 16 (19) ◽  
pp. 721-726 ◽  
Author(s):  
ZHIDONG ZHANG ◽  
ZHIGUANG LI ◽  
JINGLI LIU
Keyword(s):  
Field Theory ◽  
Theoretical Calculations ◽  
Three Dimensional ◽  
Two Dimensions ◽  
Molecular Field ◽  
Chiral Molecules ◽  
Particle Cluster ◽  
Cluster Theory ◽  
Cholesteric Phase ◽  
Molecular Field Theory

The temperature-dependent pitch of a cholesteric phase is studied using both molecular field theory and the two-particle cluster theory. The interacting chiral molecules (as derived by van der Meer et al.) are placed at the sites of a three-dimensional, simple cubic lattice with orientations confined to two dimensions. The equilibrium pitch as functions of temperature is calculated and numerical results are compared with those predicted by Monte Carlo computer simulation. The two-particle cluster theory, taking into account short-range correlations between molecules, yields improved values compared with molecular field theory.

scholarly journals Iron-Catalyzed Halogen Exchange of Trifluoromethyl Arenes

2021 ◽  
Author(s):  
Andreas Dorian ◽  
Emily Landgreen ◽  
Hayley Petras ◽  
James Shepherd ◽  
Florence Williams
Keyword(s):  
Design Of Experiments ◽  
Statistical Method ◽  
Late Stage ◽  
Theoretical Calculations ◽  
Direct Activation ◽  
Aromatic Substrates ◽  
Halogen Exchange ◽  
Iron Coordination

We report the facile production of ArCF<sub>2</sub>X and ArCX<sub>3 </sub>from ArCF<sub>3</sub> using catalytic iron(III)halides, which constitutes the first iron-catalyzed halogen exchange for non-aromatic CF bonds. Theoretical calculations suggest direct activation of C–F bonds by iron coordination. ArCX<sub>3</sub> and ArCF<sub>2</sub>X products of the reaction are synthetically valuable due to their diversification potential. In particular, bromo-, chloro-, and iododifluoromethyl arenes (ArCF<sub>2</sub>Br, ArCF<sub>2</sub>Cl, ArCF<sub>2</sub>I, respectively) provide access to a myriad of difluoromethyl arene derivatives (ArCF<sub>2</sub>R). To optimize for mono-halogen exchange, a statistical method called Design of Experiments was used. Optimized parameters were successfully applied to electron rich and electron deficient aromatic substrates, and to the late stage diversification of flufenoxuron, a commercial insecticide.

scholarly journals Structure-controllable growth of nitrogenated graphene quantum dots via solvent catalysis for selective C-N bond activation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Byung Joon Moon ◽  
Sang Jin Kim ◽  
Aram Lee ◽  
Yelin Oh ◽  
Seoung-Ki Lee ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Self Assembly ◽  
Bond Activation ◽  
Theoretical Calculations ◽  
Graphene Quantum Dots ◽  
Practical Utilization ◽  
Molecular Precursors ◽  
Chemical Structures ◽  
Simultaneous Control ◽  
Solvent Molecules

AbstractPhotophysical and photochemical properties of graphene quantum dots (GQDs) strongly depend on their morphological and chemical features. However, systematic and uniform manipulation of the chemical structures of GQDs remains challenging due to the difficulty in simultaneous control of competitive reactions, i.e., growth and doping, and the complicated post-purification processes. Here, we report an efficient and scalable production of chemically tailored N-doped GQDs (NGs) with high uniformity and crystallinity via a simple one-step solvent catalytic reaction for the thermolytic self-assembly of molecular precursors. We find that the graphitization of N-containing precursors during the formation of NGs can be modulated by intermolecular interaction with solvent molecules, the mechanism of wh ich is evidenced by theoretical calculations and various spectroscopic analyses. Given with the excellent visible-light photoresponse and photocatalytic activity of NGs, it is expected that the proposed approach will promote the practical utilization of GQDs for various applications in the near future.

scholarly journals Numerical Analysis of the Effect of Ground Dampness on Heat Transfer between Greenhouse and Ground

2021 ◽  
Vol 13 (6) ◽  
pp. 3084
Author(s):  
Grzegorz Nawalany ◽  
Paweł Sokołowski
Keyword(s):  
Thermal Energy ◽  
Transition Period ◽  
Theoretical Calculations ◽  
Ground Temperature ◽  
Temperature Fields ◽  
Test Results ◽  
Ground Temperatures ◽  
Temperature Ranges ◽  
Wet Ground ◽  
Calculation Analysis

This paper deals with the problem of the influence of ground dampness on heat exchange between greenhouse and ground. The effect of humidity on the distribution of ground temperature fields was analyzed. The analysis was performed based on the analytical numerical method in the WUFI®plus software. The computational tool was used after a validation process. Research and simulations were conducted on the example of a real single-span greenhouse located in Southern Poland. The results of indoor and outdoor air temperature measurements were used to determine the boundary conditions, while the measured ground temperatures were used to compare with the results of theoretical calculations. Three variants were used for calculation analysis, assuming different levels of ground dampness. Analysis of the test results showed that during the summer period, dry ground provides 8% more thermal energy to the interior of the greenhouse than the damp ground, and provides 30% more thermal energy than wet ground. In the transition period (autumn/spring), the ground temperature fields are arranged parallel to the floor level, while the heat flux is directed from the ground to the interior of the greenhouse, regardless of the ground dampness level. During this period, the ground temperature ranges from 4.0 °C to 13.0 °C. Beneficial effect of dry ground, which contributes to maintaining an almost constant temperature under the greenhouse floor, was found in winter.

scholarly journals Chemoselective Ring-Opening Polymerization of Bio-Renewable α-Methylene-γ-Butyrolactone via an Organophosphazene/urea Binary Synergistic Catalytic System Toward a Sustainable Polyester

2020 ◽  
Author(s):  
Yong Shen ◽  
Wei Xiong ◽  
YongZheng Li ◽  
ZhiChao Zhao ◽  
Hua Lu ◽  
...  
Keyword(s):  
Double Bond ◽  
Catalytic System ◽  
Low Temperatures ◽  
Ring Opening ◽  
Theoretical Calculations ◽  
Unsaturated Polyester ◽  
Ring Opening Polymerization ◽  
Membered Ring ◽  
Exocyclic Double Bond ◽  
Binary Catalyst

Despite the great potential of bio-renewable a-methylene-<a></a><a></a><a>g-butyrolactone</a> (MBL) to produce functional recyclable polyester, the ring-opening polymerization (ROP) of MBL remains as a challenge due to the competing polymerization of the highly reactive exocyclic double bond and the low strained five membered ring. In this contribution, we present the first organocatalytic chemoselective ROP of MBL to exclusively produce recyclable unsaturated polyester by utilizing a phosphazene base/urea binary catalyst. We show that delicate chemoselectivity can be realized by controlling the temperature and using selected urea catalysts. Experimental and theoretical calculations provide mechanistic insights and indicate that the kinetically controlled ROP pathway is favored by using urea with stronger acidity at low temperatures.

scholarly journals Enantioselective Organocatalyzed a-Amination of 1,3-Dicarbonyl Compounds in Deep Eutectic Mixtures

2018 ◽  
Author(s):  
Diego Ros Ñíguez ◽  
Pegah Khazaeli ◽  
Diego A. Alonso ◽  
Gabriela Guillena
Keyword(s):  
Catalytic System ◽  
Large Scale ◽  
Reaction Medium ◽  
Deep Eutectic Solvents ◽  
Natural Product Synthesis ◽  
Chiral Molecules ◽  
Efficient Manner ◽  
Dicarbonyl Compounds ◽  
Eutectic Mixtures ◽  
Volatile Organic

The enantioselective alpha-amination of 1,3-dicarbonyl compounds has been performed using a catalytic system based on deep eutectic solvents (DES) and chiral 2-amino benzimidazole-derived organocatalysts. This procedure avoids the use of toxic volatile organic compounds (VOCs) as a reaction medium, providing access to highly functionalized chiral molecules, which are important intermediates for the natural product synthesis, in a selective and efficient manner. Furthermore, the reaction can be performed on a large scale and recycling the catalytic system is possible for at least five times, leading to a clean, cheap, simple, and scalable procedure that meets most of the criteria required to be a green and sustainable process.

scholarly journals Iron-Catalyzed Halogen Exchange of Trifluoromethyl Arenes

2021 ◽  
Author(s):  
Andreas Dorian ◽  
Emily Landgreen ◽  
Hayley Petras ◽  
James Shepherd ◽  
Florence Williams
Keyword(s):  
Design Of Experiments ◽  
Statistical Method ◽  
Late Stage ◽  
Theoretical Calculations ◽  
Direct Activation ◽  
Aromatic Substrates ◽  
Halogen Exchange ◽  
Iron Coordination

We report the facile production of ArCF<sub>2</sub>X and ArCX<sub>3 </sub>from ArCF<sub>3</sub> using catalytic iron(III)halides, which constitutes the first iron-catalyzed halogen exchange for non-aromatic CF bonds. Theoretical calculations suggest direct activation of C–F bonds by iron coordination. ArCX<sub>3</sub> and ArCF<sub>2</sub>X products of the reaction are synthetically valuable due to their diversification potential. In particular, bromo-, chloro-, and iododifluoromethyl arenes (ArCF<sub>2</sub>Br, ArCF<sub>2</sub>Cl, ArCF<sub>2</sub>I, respectively) provide access to a myriad of difluoromethyl arene derivatives (ArCF<sub>2</sub>R). To optimize for mono-halogen exchange, a statistical method called Design of Experiments was used. Optimized parameters were successfully applied to electron rich and electron deficient aromatic substrates, and to the late stage diversification of flufenoxuron, a commercial insecticide.

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