Search results for "Addition reactions"
showing 6 items of 16 documents
A Molecular Electron Density Theory Study of the Chemoselectivity, Regioselectivity, and Diastereofacial Selectivity in the Synthesis of an Anticance…
2019
The [3 + 2] cycloaddition (32CA) reaction of an &alpha
A Molecular Electron Density Theory Study of the Synthesis of Spirobipyrazolines through the Domino Reaction of Nitrilimines with Allenoates
2019
The reaction of diphenyl nitrilimine (NI) with methyl 1-methyl-allenoate yielding a spirobipyrazoline has been studied within molecular electron density theory (MEDT) at the MPWB1K/6-311G(d) computational level in dichloromethane. This reaction is a domino process that comprises two consecutive 32CA reactions with the formation of a pyrazoline intermediate. Analysis of the relative Gibbs free energies indicates that both 32CA reactions are highly regioselective, the first one being also completely chemoselective, in agreement with the experimental outcomes. The geometries of the TSs indicate that they are associated to asynchronous bond formation processes in which the shorter distance invo…
The influence of substitution in the quinoxaline nucleus on 1,3-dipolar cycloaddition reactions
2013
The reaction mechanism of 1,3-dipolar cycloadditions of both symmetric and unsymmetric benzo-condensed diazines with a nitrilimine dipole, to give two different mono- and bis-cycloadducts, in tetrahydrofuran (THF) solution, was studied by DFT calculatio ns. The results obtained show that each 1,3-dipolar cycloaddition reaction always proceeds by a two steps mechanism, in which the first intermediate shows only one covalent bond between the beta carbon of the nitrilimine and the aromatic nitrogen of the diazine molecule. The structure and energy content of the two transition states of the two cycloaddition steps, in the case of the unsymmetric benzo-condensed diazine, nicely explains why the…
Unravelling [3+2] Cycloaddition Reactions through the Molecular Electron Density Theory
2018
Después de la primera clasificación de las reacciones 32CA en reacciones de tipo zw y pr, establecidas en el año 2014, la estructura y reactividad de los TACs más importantes utilizados en las reacciones 32CA ha sido completamente caracterizado en base a la MEDT propuesta recientemente. Entre la gran cantidad de trabajo desarrollado a lo largo de la presente tesis doctoral, se han seleccionado y discutido ocho publicaciones representativas, que permitieron caracterizar dos nuevos tipos de reactividad y consolidar la reactividad original de tipo zw. Así, dependiendo de las cuatro estructuras electrónicas diferentes de los TACs, es decir, pseudodiradical, pseudoradical, carbenoide y zwitterió…
Unveiling the Different Reactivity of Bent and Linear Three-Atom-Components Participating in [3 + 2] Cycloaddition Reactions
2021
The reactivity of a series of pairs of bent and linear three-atom-component (B-TACs and L-TACs) participating in [3 + 2] cycloaddition (32CA) reactions towards ethylene and electrophilic dicyanoethylene (DCE) have been studied within the Molecular Electron Density Theory. While the pseudodiradical structure of B-TACs changes to that of pseudoradical or carbenoid L-TACs upon dehydrogenation, zwitterionic B-TACs remain unchanged. Conceptual Density Functional Theory (CDFT) indices characterize five of the nine TACs as strong nucleophiles participating in polar reactions towards electrophilic ethylenes. The activation energies of the 32CA reactions with electrophilic DCE range from 0.5 to 22.0…
5-Carbonyl-1,3-oxazine-2,4-diones from N-Cyanosulfoximines and Meldrum’s Acid Derivatives
2020
At elevated temperatures, N-cyanosulfoximines react with Meldrum’s acid derivatives to give sulfoximines with N-bound 5-carbonyl-1,3-oxazine-2,4-dione groups. A representative product was characterized by single-crystal X-ray structure analysis. The product formation involves an unexpected molecular reorientation requiring several sequential bond-forming and -cleaving processes. peerReviewed