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.

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The bromination reaction of thieno [3,2-b]benzofuran was studied theoretically. Stationary points on the reaction potential energy profile including intermediates and transition states were successfully located employing hybrid DFT procedure at the B3LYP/6-31G* level of theory. The bromination proceeds in two steps at the C(2) carbon of thiophene ring. Initially, a π-complex forms between bromine molecule and thiophene ring. Further the π-complex with high activation barrier 69.9 kcal/mol transforms to σcomplex intermediate. Finally the σ-complex with 4.6 kcal/mol activation transforms to product 2-bromothieno[3,2-b]benzofuran.

ABSTRACT:The novel 4H-thiazolo[3,2-d]

[2,3-g] or [2,3-h]quinoline derivatives were prepared from 7-(or 8, or 9)amino-1,5-benzodiazepin-2-ones by the Doebner-von Miller quinoline synthesis. The structure of the cyclized products depends on the position of the primary amino group and on the substituents of the diazepine ring of the starting compounds. The regiochemical outcome of the reaction was estimated by calculating average local ionization energies on the molecular surface at the Density Functional Theory (DFT) level of theory.