Investigation of the mechanism of the recyclization of furans to thiophenes and selenophenes under acid-catalysis conditions. 3. Investigation of the recyclization of homologs and functional derivatives of furan. Quantum-chemical calculations of the objects of the recyclization

The kinetics of the conversion of di-, tri-, and tetraalkylfurans to the corresponding thiophenes were investigated. A correlation between the reactivities and structures of the investigated furans was established. Quantum-chemical calculations of the objects of the recyclization were made. The calculated and experimental data on the reactivities of the investigated compounds were compared. The most likely pathway of the protonation of furans in their recyclization was determined on the basis of calculations of the total energies of the protonated forms.For Communication 2 see 1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1614–1620, December, 1993.