A theoretical approach to the nucleophilic behavior of benzofused thieno[3,2-b]furans using DFT and HF based reactivity descriptors

Calculations of traditional HF and DFT based reactivity descriptors are reported for the isomeric benzofused thieno[3,2-b]furans in order to get insight into the factors determining the nature of their interactions with electrophiles. Global reactivity descriptors such as ionization energy, molecular hardness, electrophilicity, frontier molecular orbital energies and shapes, the condensed Fukui functions, total energies were determined and used to identify the differences in the stability and reactivity of benzofused thieno[3,2-b]furans. Additionally the bond order uniformity analysis, local ionization energy and electrostatic potential energy surfaces revealed structural differences of isomeric thieno[3,2-b]furans. Calculated values lead to the conclusion that heterocyclic system in thieno[3,2-b] benzofuran is more aromatic and stable than in isomeric benzothieno[3,2-b] furan. Theoretical results are in complete agreement with the experimental results and show exceptional reactivity of C(2) atom for both isomers.