ORGANIC PHOSPHORUS COMPOUNDS 82. PREPARATION, PROPERTIES AND HERBICIDAL ACTIVITY OF 2-SUBSTITUTED 5-PHENOXY- AND 5-PYRIDYLOXY PHENYL PHOSPHONIC AND PHOSPHINIC ACID DERIVATIVES

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Abstract
In the Cadogan reaction of 1,2-dinitro-4-chlorobenzene with phosphites and phosphonites the 2-nitro group is substituted but in 1,2-dinitro-4-alkoxycarbonylbenzenes the 1-nitro group is replaced exclusively (Table I and II). Extension of the Cadogan reaction to 4-phenoxy and 4-pyridyloxy substituted 1,2-dinitrobenzenes produced mainly 5-phenoxy and 5-pyridyloxy substituted 2-nitrophenylphosphonates and -phosphinates some of which show high herbicidal and plant growth regulating activity (Table III to V and Figure 1 to 4). 4- and 6-phenoxy or pyridyloxy substituted 2-nitrophenylphosphonates are herbicidally inactive. The herbicidal activity decreases from the phenoxy-phenylphosphonates to -phosphinates to pyridyloxy-phenylphosphonates when the same substitution pattern is present. The methyl esters 3a, 4a and 5a are the most active compounds in all three series. We wish to thank Ciba-Geigy's Physical Science Center for the hydrogenation experiments, the combustion analyses and for the 31P and 13C NMR spectra, and Messieurs H. Spoerri, M. Walti and M. Hartmeyer for experimental help.
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