Mechanism and Regioselectivity of the 1,3-Dipolar Cycloaddition of Methyleneamine N-Oxide with Cyclopent-3-Ene-1,2-Dione and its Aza, Oxa and Thia Analogues: A Dft Approach

Abstract

A theoretical study on the regioselectivity of 1,3-dipolar cycloaddition reactions between methyleneamine N-oxide (nitrone) and cyclopent-3-ene-1,2-dione (DPh1), pyrrole-2,3-dione (DPh2), furan-2,3-dione (DPh3) and thiophene-2,3dione (DPh4) has been carried out by means of several theoretical approaches, namely, activation energies, Houk's rule based on FMO theory and DFT reactivity indices. The calculations were performed at the DFT-B3LYP=6-31G(d) level of theory using Gaussian 03. The present analysis shows that these reactions have an NED character. Moreover, the results obtained from energetic and electronic approaches, with the exception of Gazquez -Mendez rule based on NPA analysis, confirm that 1,5-regioisomer is the major product.

Synthesis, characterization and computational studies for (2′S*,3R*,3′S*,8a′R*)‐2′,3′‐bis(ethoxycarbonyl)‐2‐oxo‐2′,3′‐dihydro‐8a′H‐spiro[indoline‐3,1′‐indolizine]‐6′‐carboxylic acid and some derivatives

“…Sustmann [35,36] classified the cycloaddition processes into three categories based on the FMO theory: (I) Normal-electron demand, or NED, which is the interaction between the HOMO dipole and LUMO dipolarophile ; (II) Inverse electron demand, or IED; and (III) which can be identified by the similarity of the HOMO and LUMO energies of the dipole = dipolarophile pair. [30,37,38] In this study, the energy gaps of HOMO/LUMO, electronic chemical potentials, and electrophilicity indices have been calculated in order to predict the NED/IED character of the 1,3-dipolar cycloaddition reaction of pyridinium salt with various oxindoles (Table 2). It demonstrates that all reactants' jHOMO dipole LUMO dipolarophile j gaps are less than their jHOMO dipolarophile LUMO dipolarophile j counterparts (see Figure 3 and Table 3).…”

“…For 1,3-dipolar cycloaddition reactions, the structures of each reactant were perfectly optimized. The energy gap (ΔE), chemical softness (S) and hardness (η), and electrophilicity index (ω) were calculated using molecular orbital theory [30][31][32] and are displayed in Table 2. The ionization energies (I), and electron affinities (A), were determined at the optimized geometry by…”