Etude des reactions de srn1—partie 10 : Action de sulfanions sur les halogenures d'aryle fonctionnalises. synthese directe de benzothiophenes et thienopyridines

Functionalized aromatic halides Ar₁XY (Ar₁ = C₆H₄, Y = OCH₃, CONH₂, CN, COCH₃, CHO, COC₆H₅) undergo S_RN1 reactions with sulphur anions ^-SR, either simple (R=C₂H₅, CH₂C₆H₅) or functionalized (R = (CH₂)₂OH, (CH₂)₂CO₂Et, CH₂CO₂Et). Products Ar₁YS^- formed from the fragmentation of the radical anion Ar₁YSR^- are related to the redox potential of the aryl moiety Ar₁Y and with the energy of the bond S-R. In the heterocyclic series (Ar₂ = pyridine, Ar₃ = quinoline) a similar relationship appears but a competitive S_N(Ar) reaction occurs for pyridine substrates bearing an electron withdrawing group. A direct synthesis of benzothiophen via S_RN1 reaction and an improved synthesis of thienopyridines based on the S_N(Ar) reaction are reported.