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 electronic and free energies associated with the different reaction pathways indicates that the 32CA reactions of the AI with these NVFH are highly meta regioselective but present a poor stereoselectivity, in agreement with the experimental observations. Finally, electron localisation function (ELF) topological analysis allows characterising the mechanism of these 32CA reactions as a non-concerted two-stage one-step mechanism.
['Ríos-Gutiérrez|Mar|M|', 'Chafaa|Fouad|F|', 'Khorief Nacereddine|Abdelmalek|A|', 'Djerourou|Abdelhafid|A|', 'Domingo|Luis R|LR|']
D001391:Azo Compounds D061565:Cycloaddition Reaction D004583:Electrons D019277:Entropy D007097:Imines D007202:Indicators and Reagents D007211:Indoles D008958:Models, Molecular D008968:Molecular Conformation D011758:Pyrroles D011789:Quantum Theory D013237:Stereoisomerism D013882:Thiosemicarbazones D014753:Vinyl Compounds
[3+2] Cycloadditions Azomethine imines Selectivity DFT calculations Molecular mechanism Vinyl pyrroles