Improved techniques for semi‐micro synthesis of radioisotope labelled thiophosphate pesticides

Radiolabelled ethanol can be incorporated into the organophosphate molecule by heating PSCl3 with the labelled alcohol. Methanol can also be incorporated in this manner, but with lower yields. The O, O‐dialkyl, phosphorochloridothionates were produced by treating O‐alkyl phosphorodiahloridothionate with the appropriate sodium alkoxide. Coupling the O, O‐dialkyl phosphorochloridothionate to a substituted phenol to form the pesticidal compounds was facilitated by the catalytic effect of silver ions. The catalyzed coupling reaction was found to be compatible with hdroxyllated heterocyclic compounds, and with phenols containing nitro‐, mercapto‐, alkyl‐, and cyano‐substituents. The reaction was not successful, however, with chloro‐substituted phenols The coupling reaction was also found to be useful in synthesizing EPN, a phosphonothionate pesticide. The coupling reaction does not appear to be useful for the synthesis of oxons, the analogous phosphate compounds.