DFT calculations on 1,3-dipolar cycloaddition

reactions of indenone

N. Benkaddour1,2*, J. A. Dobado1, A. Sedqui2

1 Grupo de Modelización y Diseño Molecular, Departamento de Química Orgánica,

Campus Fuentenueva, Universidad de Granada, 18071-Granada, Spain

2Departament de Chimie, Faculte des Sciences,

Université Abdelmalek Essaadi, BP2121-Tetuan, Morocco

* Corresponding author. E-mail : nbenka@fst.ac.ma

Received : 14 November 2003; revised version accepted :10 September 2003

Abstract

Density functional theory (DFT) calculations at the B3LYP/6-311G*//B3LYP/6-311G* theoretical level have been performed to study the 1,3-dipolar cycloaddition reactions between indenone (1) and different 1,3-dipoles (diazomethane and N-methyl C-methoxy carbonyl nitrilimine, compounds 2 and 3, respectively). The geometrical and energetic properties were analysed for the different reactives, transition states and cycloadducts formed (compounds 4-11). The reactions proceed in the gas-phase by an asynchronous concerted mechanism, yielding different regiochemistry dependent on the 1,3-dipole chosen, although with dipole 3 some degree of synchrony was found in the formation of cycloadduct 5. The 1,3-DC between 1 and 3 was regioselective, being the cycloadduct 11 favoured against 9. The NMR chemical shift parameters (GIAO method) were also calculated for the reactives and cycloadducts.

Keywords: Indenone; DFT; 1,3-dipolar cycloaddition; Theoretical calculations; FMO approach.

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