Synthesis and herbicidal activity of novel pyrazolo[3,4-d]pyrimidin-4-one derivatives containing aryloxyphenoxypropionate moieties

The 6-(4-alkoxycarbonylalkoxy)phenoxy-3-alkylthio(alkylsulfonyl)-1-phenyl-5-(substituted phenyl)pyrazolo[3,4-d]pyrimidin-4-ones 6 and 7 have been synthesized via the tandem aza-Wittig and annulation reactions of the corresponding iminophosphoranes 4, aromatic isocyanates, and substituted phenols 2 in 52–98% yields. Their structures were clearly verified by spectroscopic data (IR, 1H NMR, 13C NMR, MS, and elemental analysis or X-ray diffraction crystallography). And the results of preliminary bioassay indicated that these title compounds possess potential herbicidal activity against the root of rape and barnyard grass.