Alkylphosphinates IIIA-IIIG

SAR analyzes of the relationship between enzyme inhibition and herbicidal activity conducted by Baillie et al. showed that the replacement of methoxyl in acylphosphonate 1-1 by methyl to produce acylphosphinate 1-2, which indeed led to a great improvement in inhibitoiy potency and herbicidal activity. Considering that 1-2 had stronger enzyme inhibition and herbicidal activity than 1-1, it was expected that alkylphosphinates in might have more powerful inhibition and herbicidal activity than the corresponding alkylphosphonates. The preliminary bioassay showed that most of inC—niG possessed moderate to good herbicidal activity. 

three series of phosphinates including O-methyl [l-(2-nitrophenoxyacetoxy) alkyl]methylphosphinates niA, O-methyl [l-(2-chloro-4-nitrophenoxyacetoxy) 

Furthermore, the introduction of heterocycle groups, such as thienyl or pyridyl group into parent compounds usually to improve the biological activity of compounds [11-14]. Hence, thienyl or pyridyl group as was intrcxluced into parent compound IC. Two series of (5-methyl [1-(substituted phenoxyacetoxy)-l-(thien-2-yl)methyl] 

The synthetic methods of IIIA-IIIG and the intermediates are described as follows. 

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Scheme 1.29 Design of alkylphosphinates IIIA-IIIG by modification of IC-IJ...

These results encouraged us to design and prepare monosalts of alkylphosphinate to compare the herbicidal activity and enzymatic-selectivity between alkyl-phospinate and their phosphonate counterparts. Therefore, a novel series of sodium [1-(substituted phenoxyacetoxy)alkyl]methylphosphinates IIIH was further designed through replacing the MeO group in IIIA-IIIG by NaO (Scheme 1.30). 

Scheme 1.30 Design of sodium salts of alkylphosphinic acids IIIH by modification of IIIA-IIIG...

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