Electrocyclic aromatic substitution by the diazo group. Part 5. The reactions of α-(2-arylthienyl)diazoalkanes

Abstract

3-Diazoalkyl-2-phenyl- and 2-diazoalkyl-3-phenyl-thiophenes have been generated from tosylhydrazone sodium salts. Neither species undergoes 6π or 8π electrocyclisation reactions of the diazo group and both give only carbene-derived products. The products from the 3-diazoalkylthiophenes (1; R = H, Me) depend on the nature of R, thus, (16) gives the carbene ‘dimer’ and azine while (21) reacts via an intramolecular path to give (22). The carbenes from the 2-diazoalkylthiophenes react via ring cleavage to give oligomers of γ,δ-acetylenic thioaldehydes.