A Convenient Synthesis and Herbicidal Activity of<i>N</i>-phosphonoalkylpyrazolo[4,3-<i>e</i>][1,2,4]-triazolo[1,5-<i>d</i>]pyrimidines

Abstract

An important building block, diethyl [(5-amino-4-cyano-3-methylsulfanyl-pyrazol-1-yl)–(4-fluorophenyl)methyl] phosphonate (3) was efficiently synthesized via the condensation of 1-hydrazino-1-(4-fluorophenyl)methyl phosphonate (1) with 2-[bis(methylthio)methylene]malononitrile (2).3 reacted with triethyl orthoformate to afford diethyl [(4-cyano-5-ethoxymethyleneamino-3-methylsulfanyl-pyrazol-1-yl)-(4-fluorophenyl)methyl] phosphonate (4), which reacted with various acyl hydrazines in refluxing 2-methoxyethanol to provide the target compounds (5) in good yields directly. The results of preliminary bioassay indicated that compounds 5 possess potent herbicidal activity against the roots of monocotyledonous (barnyard grass) and dicotyledonous (oil rape) plants, and could be further developed as potential herbicides.