Synthesis of 2,5-bis(phosphinoylmethyl)- and 2,5-bis(thiophosphinoylmethyl) -thiophenes

The 2,5-bis(phosphinoylmethyl)-thiophenes [(Oct)(EtO)P(O)CH ₂]₂C₄H₂S and [(Ph)(EtO)P(O)CH ₂]₂C₄H₂S are obtained from the appropriate phosphites, RP(OEt)₂ (R=Oct, Ph) and (BrCH ₂)₂C₄H₂S by using Arbusov reaction conditions. The analog [(Oct)₂P(O)CH₂]₂C ₄H₂S is more conveniently obtained via the reaction of the phosphono-Grignard reagent (Oct)₂P(O)MgBr and (BrCH ₂)₂C₄H₂S. An improved alternate Arbusov synthesis of the known [Ph₂P(O)CH₂] ₂C₄H₂S is described along with its conversion to [Ph₂P(S)CH₂]₂C₄H₂S via Lawesson chemistry. The new compounds are characterized by MS, IR and NMR methods, and the molecular structures of [Ph₂P(O)CH₂] ₂C₄H₂S and [Ph₂P(S)CH ₂]₂C₄H₂S have been confirmed by single crystal X-ray diffraction methods.