Preparation of Phosphate and Pyrophosphate Esters by the Metal-catalyzed Reaction of 8-Quinolyl Phosphates

In the presence of Cu (II) ion, alkyl 8-quinolyl hydrogen phosphates (alkyl=ethyl, cyclohexyl, and benzyl) converted into the corresponding P1, P2-disubstituted pyrophosphates with formation of 8-hydroxyquinoline-Cu (II) chelate in anhydrous pyridine. When this reaction was carried out in pyridine containing alcohols (R'=ethyl, amyl, cyclohexyl, and benzyl), corresponding dialkyl hydrogen phosphates (R-R'=ethyl-cyclohexyl, amyl-cyclohexyl, cyclohexyl-benzyl, and ethyl-benzyl) were formed as a sole product. The factors (water content, solvent, metal ion) which affect this metal-catalyzed reaction were examined, and a possible mechanism for the reaction was presented.