Proton‐Ionizable crown compounds. 8. Synthesis and structural studies of macrocyclic polyether ligands containing a 4‐thiopyridone subcyclic unit

Three new proton‐ionizable macrocyclic polyether ligands containing the 4‐pyridone subcyclic group have been prepared. Two of these ligands contain lipophilic n‐octyl substituents, the other ligand contains a phenyl substituent. The 15‐crown‐5 ligand containing both a 4‐pyridone subcyclic unit and an n‐octyl substituent selectively transported lithium cations in a water‐methylene chloride‐water bulk liquid membrane system. Five crown compounds containing the 4‐pyridone subcyclic unit were converted to the 4‐thiopyridono‐crown compounds when treated with Lawesson's Reagent. The crystal structure of 4‐thiopyridono‐18‐crown‐6 shows a carbon‐sulfur double bond and a molecule of water hydrogen bonded inside the macrocycle cavity.