Thermal Phenomena Under Microwave Field in the Organic Synthesis Processes: Application to the Diels Alder Reaction

1996 ◽  
Vol 430 ◽  
Author(s):  
R. Saillard ◽  
M. Poux ◽  
M. Audhuy-Peaudecerf
Keyword(s):  
Electric Field ◽  
Microwave Heating ◽  
Field Intensity ◽  
Electric Field Intensity ◽  
Thermal Fluctuations ◽  
Alder Reaction ◽  
Diels Alder ◽  
Conventional Heating ◽  
Medium Temperature ◽  
Diels Alder Reaction

AbstractThe influence of the microwave heating on chemical reactions were investigated. The kinetic of the Diels Alder reaction were studied under Microwave irradiation at a frequency of 2.45 GHz in a single mode cavity and were compared to the kinetic obtained by a conventional heating. Experiments were carried out in a liquid solvent in order to have a better control of the medium temperature measurement. In a second part, the presence of a catalytic solid phase was introduced. Some thermal fluctuations which are due to an heterogeneity of the electric field were detected in the medium. They reduce the precision of the results and cause problems of experimental reproducibility. A thermoluminescent material allow a good visualisation of these phenomena.In addition, the profiles of the electric field intensity were modelled by a 2D finite elements method in our reactor in the presence of a solvent. Despite the small size of the sample and the use of a monomode cavity which both limited the heterogeneities of the medium temperature, we showed a great heterogeneity of the electric field intensity and as a result the heterogeneity of the temperature in our sample.In order to avoid these phenomena which induce a lack of reproducibility, a stirring device was developed.The values of the kinetics obtained under the 2 heating modes with the introduction of the stirring device. So, it induces a good control of the medium temperature.All those investigations prompted us to the conclusion that there is no difference between microwave heating and a classical heating in the studied reaction.

scholarly journals Heterogeneous Intramolecular Electric Field as a Descriptor of Diels-Alder Reactivity

2020 ◽  
Author(s):  
Matthew Hennefarth ◽  
Anastassia N. Alexandrova
Keyword(s):  
Electric Field ◽  
Electron Density ◽  
Electric Fields ◽  
Alder Reaction ◽  
Diels Alder ◽  
Charge Movement ◽  
External Electric Fields ◽  
Topological Features ◽  
Diels Alder Reaction ◽  
Kinetics Of

<div> <div> <div> <p>External electric fields have proven to be an effective tool in catalysis, on par with pressure and temperature, affecting the thermodynamics and kinetics of a reaction. However, fields in molecules are complicated heterogeneous vector objects, and there is no universal recipe for grasping the exact features of these fields that implicate reactivity. Herein, we demonstrate that topological features of the heterogeneous electric field within the reactant state, as well as of the quantum mechanical electron density – a scalar reporter on the field experienced by the system – can be identified as rigorous descriptors of the reactivity to follow. We scrutinize specifically the Diels-Alder reaction. Its 3-D nature and the lack of a singular directionality of charge movement upon barrier crossing makes the effect of the electric field not obvious. We show that the electric field topology around the dienophile double bond, and the associated changes in the topology of the electron density in this bond are predictors of the reaction barrier. They are also the metrics by which to rationalize and predict how the external field would inhibit or enhance the reaction. The findings pave the way toward designing external fields for catalysis, as well as reading the reactivity without an explicit mechanistic interrogation, for a variety of reactions. </p> </div> </div> </div>

Microwave-specific acceleration of a retro-Diels–Alder reaction

2020 ◽  
Vol 56 (76) ◽  
pp. 11247-11250
Author(s):  
Michael A. Frasso ◽  
Albert E. Stiegman ◽  
Gregory B. Dudley
Keyword(s):  
Microwave Heating ◽  
Alder Reaction ◽  
Thermal Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction

Selective microwave heating in a viscous solvent accelerates a thermal reaction beyond temperature-based expectations.

scholarly journals Electric field–catalyzed single-molecule Diels-Alder reaction dynamics

2021 ◽  
Vol 7 (4) ◽  
pp. eabf0689
Author(s):  
Chen Yang ◽  
Zitong Liu ◽  
Yanwei Li ◽  
Shuyao Zhou ◽  
Chenxi Lu ◽  
...  
Keyword(s):  
Electric Field ◽  
Single Molecule ◽  
Field Experiments ◽  
Alder Reaction ◽  
Diels Alder ◽  
Charge Transfer Complexes ◽  
Label Free ◽  
Diels Alder Reaction ◽  
Zwitterionic Intermediate

Precise time trajectories and detailed reaction pathways of the Diels-Alder reaction were directly observed using accurate single-molecule detection on an in situ label-free single-molecule electrical detection platform. This study demonstrates the well-accepted concerted mechanism and clarifies the role of charge transfer complexes with endo or exo configurations on the reaction path. An unprecedented stepwise pathway was verified at high temperatures in a high-voltage electric field. Experiments and theoretical results revealed an electric field–catalyzed mechanism that shows the presence of a zwitterionic intermediate with one bond formation and variation of concerted and stepwise reactions by the strength of the electric field, thus establishing a previously unidentified approach for mechanistic control by electric field catalysis.

scholarly journals Heterogeneous Intramolecular Electric Field as a Descriptor of Diels-Alder Reactivity

2020 ◽  
Author(s):  
Matthew Hennefarth ◽  
Anastassia N. Alexandrova
Keyword(s):  
Electric Field ◽  
Electron Density ◽  
Electric Fields ◽  
Alder Reaction ◽  
Diels Alder ◽  
Charge Movement ◽  
External Electric Fields ◽  
Topological Features ◽  
Diels Alder Reaction ◽  
Kinetics Of

<div> <div> <div> <p>External electric fields have proven to be an effective tool in catalysis, on par with pressure and temperature, affecting the thermodynamics and kinetics of a reaction. However, fields in molecules are complicated heterogeneous vector objects, and there is no universal recipe for grasping the exact features of these fields that implicate reactivity. Herein, we demonstrate that topological features of the heterogeneous electric field within the reactant state, as well as of the quantum mechanical electron density – a scalar reporter on the field experienced by the system – can be identified as rigorous descriptors of the reactivity to follow. We scrutinize specifically the Diels-Alder reaction. Its 3-D nature and the lack of a singular directionality of charge movement upon barrier crossing makes the effect of the electric field not obvious. We show that the electric field topology around the dienophile double bond, and the associated changes in the topology of the electron density in this bond are predictors of the reaction barrier. They are also the metrics by which to rationalize and predict how the external field would inhibit or enhance the reaction. The findings pave the way toward designing external fields for catalysis, as well as reading the reactivity without an explicit mechanistic interrogation, for a variety of reactions. </p> </div> </div> </div>

Indole synthesis by palladium-catalyzed tandem allylic isomerization – furan Diels–Alder reaction

2017 ◽  
Vol 15 (34) ◽  
pp. 7093-7096 ◽  
Author(s):  
Jie Xu ◽  
Peter Wipf
Keyword(s):  
Microwave Heating ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction ◽  
Palladium Catalyzed ◽  
Indole Synthesis

4-(Furan-2-ylamino)but-2-en-1-yl acetates are converted to substituted indoles under microwave heating in the presence of catalytic tetrakis(triphenylphosphine)palladium(0) and triisopropylphosphite.

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