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Eccles, Peter John (1984) The synthesis and fungicidal activity of some novel phosphoramidates. Doctoral thesis, Polytechnic of North London.
The synthesis of novel fungicidal phosphoramidates was the main objective of the present work. Various fungitoxic substituents were included in their structure together with a trichloromethyl group which has been shown to enhance fungicidal activity in other compounds.
Fourteen compounds containing the 1,1,1-trichloro-2-(diethoxyphosphinylamino)ethyl group were synthesised from the condensation product of chloral and diethyl phosphoramidate. These included one derivative which also contained the 1,1,1-trichloro-2-(bisdimethylaminophosphinyl- amino)ethyl group. Other fungitoxic substituents introduced into the molecular structure of the compounds include imidazole 1,2,4-triazole, morpholine, piperazine, dimethyldithiocarbamate, diethyldithiocarbamate, xanthate and 5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxylate.
Preliminary investigations were carried out into the synthesis of compounds containing the 1,1,1-trichloro-2-(bisdimethylaminophosphinyl- amino)ethyl group via the condensation of chloral with N,N,N',N'-tetramethyIphosphoric triamide but these proved to be unfruitful due to side reactions.
Similar side reactions occurred, but to a lesser extent, when chloral was condensed with 0-ethyl N, N-dimethylphosphorodiamidate, and one derivative was prepared containing the 1,1,1-trichloro-2-(ethoxydimethylaminophosphinylamino)ethyl group.
The fifteen potential fungicides were characterised by elemental analysis, nuclear magnetic resonance spectrometry, mass spectrometry, and infra-red spectroscopy.
Their fungicidal activity was assessed in vitro against spores of Fusarium culmorum, Fusarium oxysporum, Helminthosporium sativum, Helminthosporium avenge, Septoria nodorum, Ophiobolus graminis, Piricularia oryzoe and Rhizoctania solani and in vivo against Dreschlera teres and Septoria nodorum. These pathogens were chosen because they affect economically important crops, mainly wheat and barley or, in the case of P. oryzae, rice. All the compounds showed some fungicidal activity, the best results being shown by 0,0-diethyl-N-2,2,2-trlchloro-1-(dimethylthiocarbamoylthio)ethyl phosphoramidate against Fusarium culmorum.
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