Salts of alkylphosphonates

Indeed, some mono sodium salts of 1-(substituted phenoxyacetoxy)alkylphos-phonic acids showed much higher inhibitory activity against plant PDHc El and 

1 Alkali Metal Salts of 0-Alkyl Alkylphosphonic Acids IIA-IIE 

---

Alkylation of dialkylphosphorous salts by dialkyl phosphites and by phos-phonic diesters has been mentioned above (page 729). The latter reaction can be used for nearly quantitative preparation of salts of alkylphosphonic monoesters, by converting the dialkyl phosphite into its sodium salt and heating this in a sealed tube with a catalytic amount of a phosphonic diester containing the same alkyl group.329 Further, when heated alone, sodium dialkyl phosphites afford, according to the conditions, sodium alkylphosphonates or disodium phosphonates and dialkyl phosphonates.330... 

Compared with alkylphosphonates IC and monosalts IIA-IIE, several series of monosalts of alkylphosphonic acids IIF-IIH demonstrated higher inhibitory activity against monocotyledonous weeds in jxjst-emergence application. IIF-1, IIG-1, and IIH-1 could provide 50-80 % control at 150 g ai/ha for the monocot weeds. However, their corresponding phosphonate IC-22 and monosodium salt IIB-2 showed no activity under the same test conditions. We considered these alkali metal salts of alkylphosphonates or alkylphosphonic acids HA-IIH was a new OP herbicide lead which should be worth further optimization. 

Scheme 1.27 Design of alkali metal salts of alkylphosphonates or alkylphosphonic acids TTA-TTH by modification of IC...

Based on the bioisosterism, the salts of alkylphosphonates lA or IC were assumed to have a more powerful inhibitory effect against plant PDHc El and better h iddal activity than the corresponding alkylphosphonates, because sodium D-methyl acety-Iphosphonate 1-1 has been reported as a powerful PDHc El inhibitor [1]. Five series of novel alkali metal salts of D-alkyl 1-(substituted phenoxyacetoxy)alkylphosphonates IIA-IIE were first designed as potential plant PDHC El inhibitors. IIA-IIE could be easily synthesized from corresponding D,D-dialkyl 1-(substituted phenoxyacetoxy) alkylphosphonates lA or IC in one step. It was also expected that 1-(substituted phenoxyacetoxy)alkylphosphonic acids (Scheme 3.2) could have better herbicidal activity, because they were more analogous to pymvic acid which acted as the substrate of PDHc. However, 1-(substituted phenoxyacetoxy)alkylphosphonic acids were not stable for long-time storage. 

Comparing the herbicidal activity of salts of alkylphosphonic acids, in Table 3.18, the sodium salts of alkylphosphonic acids seem to have better activity than potassium and lithium salts of alkylphosphonic acids. Pre-emergence and post-emergence... 

As stated in Chaps. 2 and 3, 1-substituted alkylphosphonates and salts of alkylphosphonates, such as lC-22 (clacyfos, HW02), lG-21 (HWS), and IIJ-24 were found to display promising h bicidal activity and good selectivity for development as a potential herbicide. These results also encouraged us for further exploration on alkylphosphinates based on these alkylphosphonates. Therefore, we are very interested to design novel 1-(substituted phenoxyacetoxy) alkylphosphinates and examine their herbicidal activity. 

Alkali metal salts of alkylphosphonic acids TTF-IIH could be obtained from corresponding alkylphosphonic acids M9 by the treatment with an equimolar inorganic base, such as hydrated lithium hydroxide, sodium hydroxide or potassium carbonate (Scheme 9.12). 

Scheme 9.12 Synthesis of alkali metal salts of alkylphosphonic acids IIF-IIH...

---