Abstract: Twenty two hew compounds with the general formula:   have been prepared through the cyclization of alkyl N-alkyl alkylcarbamoylphos-phonamidates with (4-substituted)phenyl dichlorophosphines in the presence of triethylamina and then sulfurization by sulfur. One of these syntheses, in which 6 was obtained by direct sulfurization without the separation of 5, was used.The structures of the products were proved by ¹H, ³¹P NMR, IR, MSandelemental analysis. ³¹PNMR chemical shift differences Δδ_P and IR wavenumberdifferencesΔv_P=s showed themselves to correlate with the Taft constant (σ⁰).respectively This finding was discussed in terms of possible (p→d)π backbonding. It was found that some of these compounds have herbicidal and fungic-idal activities.

Key words: Synthesis, Isomer, Linear relationship, Bioassay