Analysis of the possibility and molecular mechanism of carbon dioxide consumption in the Diels-Alder processes

Abstract

The large and significant increase in carbon dioxide concentration in the Earth’s atmosphere is a serious problem for humanity. The amount of CO2 is increasing steadily which causes a harmful greenhouse effect that damages the Earth’s climate. Therefore, one of the current trends in modern chemistry and chemical technology are issues related to its utilization. This work includes the analysis of the possibility of chemical consumption of CO2 in Diels-Alder processes under non-catalytic and catalytic conditions after prior activation of the C=O bond. In addition to the obvious benefits associated with CO2 utilization, such processes open up the possibility of universal synthesis of a wide range of internal carboxylates. These studies have been performed in the framework of Molecular Electron Density Theory as a modern view of the chemical reactivity. It has been found, that explored DA reactions catalyzed by Lewis acids with the boron core, proceeds via unique stepwise mechanism with the zwitterionic intermediate. Bonding Evolution Theory (BET) analysis of the molecular mechanism associated with the DA reaction between cyclopentadiene and carbon dioxide indicates that it takes place thorough a two-stage one-step mechanism, which is initialized by formation of C–C single bond. In turn, the DA reaction between cyclopentadiene and carbon dioxide catalysed by BH3 extends in the environment of DCM, indicates that it takes place through a two-step mechanism. First path of catalysed DA reaction is characterized by 10 different phases, while the second by eight topologically different phases.

On the Question of Zwitterionic Intermediates in the [3 + 2] Cycloaddition Reactions between C-arylnitrones and Perfluoro 2-Methylpent-2-ene

“…In particular, for both MCA and MCB, the C3–C4 distances were 3.82 Å, whereas the C5-O1 distances were about 2.7 Å. Thus, the interatomic distances were beyond the typical range for the corresponding distances at transition states [ 36 , 37 , 38 , 39 , 40 ]. It should be underlined that these MC s did not exhibit the nature of electron density transfer complexes [ 41 ].…”

“…This analysis was performed based on CDFT reactivity indices ( Table 1 ) [ 34 ]. A similar approach was recently used to explain the course of many different types of cycloaddition processes [ 35 , 36 , 37 , 38 ]. It was found that nitrones 1 exhibited a moderately electrophilic nature.…”

On the Mechanism of the Synthesis of Nitrofunctionalised Δ2-Pyrazolines via [3+2] Cycloaddition Reactions between α-EWG-Activated Nitroethenes and Nitrylimine TAC Systems

“…The regioselectivity of polar processes of non-symmetric reagents can be specified through interaction between the most electrophilic center of the electrophile and the most nucleophilic ones of the nucleophile. For this purpose, electrophilic P k + and nucleophilic P k − Parr functions, derived from the changes of spin electron density reached via the GEDT process from the nucleophile to the electrophile, can be used as a powerful tool in the study of the local reactivity [42][43][44]. According to the nucleophilic P k − Parr functions of nitrylimine components 1a,c,e and the electrophilic P k + Parr functions of nitroethanes 2a-c in order to characterize the most nucleophilic and electrophilic centers of the species involved in this polar 32CA reaction were analyzed (Figure 1).…”

On the Question of Stepwise [4+2] Cycloaddition Reactions and Their Stereochemical Aspects

“…Even with a relatively active nucleophile, which is cyclopentadiene 1, it does not undergo the cycloaddition reaction. DFT calculations have shown that, in the gas phase, such a process would be carried out according to a one-step mechanism, through a transition state of relatively high synchronicity (Scheme 25) [87]. However, the energy of this transition state is so high that it excludes the likelihood of effective conversion of the reaction components under normal conditions.…”