THE SYNTHESIS OF PHOSPHORAMIDOTHIOATES AND THEIR QUANTITATIVE STRUCTUREACTIVITY CORRELATIONS

Abstract

O-Aryl O-ethyl N-isopropyl phosphoramidothioates (Ⅰ) have herbicidal activity. In order to study the relationship between structures and activities of these compounds, more than thirty compounds (Ⅰ) have been prepared by the reaction of O-aryl O-ethyl phosphorochloridothioates with isopropylamine in the presence of 40% NaOH at 0℃. The intermediates, phosphorochloridothioates, were prepared separately from a large excess of O-ethyl Phosphorodichloridothioate and various substituted phenols in the presence of 40% NaOH and a catalyrical amount of Et_3N at 0—5℃. As a result, higher purity and good yields were obtained.It was found that the activity of these compounds was highly dependent upon the substituents attached to the benzene ring with respect to the characteristic parameters π, E_s, σ and F by using Hansch's equation.It was indicated that hydrophobic (π), steric (E_s), and electronic (σ and F) effects of the substituents on the ring in those molecules seem to be of considerable importance in determining their biological activity.By replacing π with △R_m and a and F with △δ_p, respectively, in regression analysis a better correlation was obtained. Both △R_m and △δ_p were experimental data. The former was calculated from R_f measured with reversed-phase thin-layer chromatography and the latter was obtained from the difference between the chemical shifts of the ~(31)P NMR of compounds(Ⅰ) and that of the parent compound.