A recent paper by Yoshitake et. a1.l describing the synthesis of carbon-14 labeled optically active 0-aryl 0-ethyl phenylphosphonothioates prompts us to report on our preparation of two labeled substances of the same compound class, although not in their optically active form. PhosvelTM, 0-(4-bromo-2,5dichlorophenyl) O-methyl phenylphosphonothioate and EPNTM, O-(4-nitrophenyl) 0- ethyl phenylphosphonothioate were both prepared with uniformly labeled phenyl rings in the acid moiety.
The overall synthetic scheme utilized for the preparation of both PhosvelTM-Both compounds were (phenyl-14Cg) -5 and EPNTM-(phenyl-14Cg) 5 is depicted below. prepared from the same intermediate, phenyl-14Cg-phosphonothioic dichloride (2).
Uniformly l 4 C-labeled benzene and phosphorus trichloride in the presence of aluminum chloride2 formed the complex 1, which was sulfurized without isolation to give intermediate 2.
presence of 5-ethyl-2-meth~lpyridine~ led to the phosphonochloridothioates 2. and -4 . The final condensation of these thionophosphine ester chlorides with the appropriate phenols was run in a two phase system with the aid of a phase transfer reagent. This approach, used before for the synthesis of phosphate esters4, simplifies this last condensation. refluxing in a dry inert solvent, the mixtures were stirred at ambient temperature for the short times indicated in the experimental section.
Compound Litself was obtained in a two step one-pot reaction.
Reaction of 2 with the respective alcohols in the Instead of the usual prolonged