Synthesis of polyfunctional stable nitrile oxides of the thiophene series and their relative reactivities in 1,3-dipolar cycloaddition with styrene

Stable 2-alkylthio- and 2-alkylsulfonylthiophene-3-carbonitrile oxides that contain various functional groups in the 4 and 5 positions of the thiophene ring (Br, OCH₃, SCH₃, SO₂CH₃) were synthesized. It is shown that the introduction of electron-acceptor substituents into any position of the ring of thiophene-3-carbonitrile oxides gives rise to acceleration of cycloaddition to styrene. The reactivities of o-substituted thiophene-3-carbonitrile oxides of the thiophene series in 1,3-dipolar cycloaddition reactions are determined by the overall effect of the electronic and steric factors of the substituents.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1620–1628, December, 1989.