CH595763

1435333 Thiophosphonic acid esters HOECHST AG 29 Oct 1973 [4 Nov 1972] 50224/73 Heading C2P The invention comprises esters of the formula wherein R is C 1 -C 4 alkyl, C 1 -C 4 haloalkyl, C 5 -C 6 -cycloalkyl or -cycloalkenyl, phenyl optionally substituted by chlorine, methyl, ethyl or methoxy, or is bicycloheptyl or bicycloheptenyl, R 1 is C 1 -C 12 alkyl optionally substituted by halogen, nitro, or CN or by a radical of the formula -P(O)(OR 3 ) 2 , -P(O)(R 3 )(OR 3 ) or P(O)(R 3 ) 2 wherein R 3 is methyl or ethyl, or R 1 is C 3 -C 4 alkenyl or -alkynyl, C 2 -C 6 alkoxyalkyl, an alkyl (C 1 -C 3 ) mercapto-alkyl, C 5 -C 6 cycloalkyl, phenyl, halophenyl, trifluoromethylphenyl or benzyl or a radical of the formula wherein R 2 is an alkyl or alkoxyalkyl group having up to 4 carbon atoms or a phenyl or halophenyl group, R is as defined above and X and Y are O or S. The esters are obtained by reacting a compound (III) or salt thereof with a compound wherein Hal is Cl or Br, the reaction being carried out in the presence of an acid binding agent when the compound III is used in the free acid form. When Y in compound III is sulphur the compound may be formed in situ in the form of a salt by reacting a dithiophosphonic acid anhydride R-PS 2 with either (a) an alcoholate: MeOR, where Me is an alkali metal, (b) a compound: HYR 1 and a tertiary organic base, or (c) a hydroxyl compound R 1 OH and an alkali metal hydroxide MeOH. The products have pesticidal properties and may be used as active ingredients in conventional pesticidal compositions.