A molecular electron density theory study of the [3 + 2] cycloaddition reaction between an azomethine imine and electron deficient ethylenes

A DFT study of the role of the Lewis acid catalysts in the [3 + 2] cycloaddition reaction of the electrophilic nitrone isomer of methyl glyoxylate oxime with nucleophilic cyclopentene

The molecular mechanism and stereoselectivity of the BF3 Lewis acid catalyzed [3 + 2] cycloaddition (32CA) reaction between C-methoxycarbonyl nitrone and cyclopentene has been theoretically studied using DFT methods at the MPWB1K/6-31G(d) computational level. The BF3 catalyst accelerates the 32CA reaction by decreasing the activation energy leading to the formation of the trans cycloadduct as the kinetic product, in agreement with the experimental data. Inclusion of solvent effects slightly increases the activation energy and decreases the exothermic character of the 32CA reaction as a consequence of a better solvation of nitrone than the transition state and the cycloadduct. The use of the…

A DFT study of the mechanism and selectivities of the [3 + 2] cycloaddition reaction between 3-(benzylideneamino)oxindole and trans -β-nitrostyrene

The mechanism and regioselectivities and stereoselectivities of the [3 + 2] cycloaddition (32CA) reaction of 3-(benzylideneamino) oxindole (AY) and trans-β-nitrostyrene have been studied using both B3LYP and ωB97XD density functional theory methods together with the standard 6-31G(d) basis set. Four reactive pathways associated with the ortho and meta regioselective channels and endo and exo stereoselective approaches modes have been explored and characterized. While the B3LYP functional fails to predict the experimental regioselectivity, the ωB97XD one succeeds to predict the experimentally observed meta regioselectivity favoring the formation of meta/endo cycloadduct as the major isomer. …

A DFT study of [3 + 2] cycloaddition reactions of an azomethine imine with N-vinyl pyrrole and N-vinyl tetrahydroindole

The mechanism and selectivities of the [3+2] cycloaddition (32CA) reactions of azomethine imine (AI) 8 with two N-vinyl five-membered heterocycles (NVFH), 9a and 9b, have been theoretically studied using DFT methods at the MPWB1K/6-31G(d) computational level. The possible ortho/meta regio- and endo/exo stereoselective channels were explored and characterised. The low polar character of these 32CA reactions, which is the consequence of the high nucleophilic character of both reagents, as well as the non-effective reactivity of these NVFH as nucleophiles, accounts for the high calculated activation energies, 16.1 (9a) and 16.8 (9b) kcalmol-1 in chlorobenzene. Analysis of the relative electron…

The role of the trifluoromethyl group in reactivity and selectivity in polar cycloaddition reactions. A DFT study

Abstract The role of the trifluoromethyl group in reactivity, regio-, and stereoselectivity in cycloaddition reactions has been analyzed by studying the 1,3-dipolar cycloaddition (13DC) reactions of nitrone 4 with 3,3,3-trifluoro-1-nitropropene 7b and 3,3,3-trifluoro-2-nitropropene 14 using density functional theory (DFT) methods at the B3LYP/6-311G(d) level. The recent M06-2X functional has also been evaluated but, although the thermodynamic performance is improved, the kinetic data are not necessarily better than those obtained by the popular B3LYP functional for cycloaddition reactions. Four reactive channels associated with the meta and ortho regio- and endo and exo stereoselective appr…

Non-classical CH⋯O hydrogen-bond determining the regio- and stereoselectivity in the [3 + 2] cycloaddition reaction of (Z)-C-phenyl-N-methylnitrone with dimethyl 2-benzylidenecyclopropane-1,1-dicarboxylate. A topological electron-density study

The role of the ester groups in the regio- and stereoselectivities of the zw-type [3 + 2] cycloaddition (32CA) reaction of C-phenyl-N-methylnitrone with dimethyl 2-benzylidenecyclopropane-1,1-dicarboxylate (BCPC) has been studied using DFT methods at the MPWB1K/6-31G(d) level. The possible ortho/meta regioisomeric channels and the endo/exo stereoselective approach modes were explored and characterized. Analysis of the relative energies associated with the different reaction pathways indicates that the presence of the two CO2Me groups in the cyclopropane ring has a remarkable effect on selectivities favouring the ortho/endo path, in good agreement with the experimental data. Inclusion of sol…