GB779449A - New organic phosphorus-containing derivative, process for its preparation and compositions containing it - Google Patents

Abstract

The invention comprises as a new product: 2-(0,0 - dimethylthiolophosphorylmethyl) - 5 - methoxy-4-pyrone of the formula <FORM:0779449/IV(b)/1> It may be obtained by reacting a salt of the general formula (CH3O)2P(O).S.Me where Me represents an alkali metal such as sodium or potassium with a derivative of g -pyrone of the general formula <FORM:0779449/IV(b)/2> where Z represents a halogen atom or a reactive ester group such as a sulphate or sulphonate group. The reaction is preferably effected in an organic solvent such as an aliphatic alcohol or ketone and it is preferred to employ a reaction temperature of 50 DEG to 100 DEG C. and more preferably at about the boiling point of the solvent employed. In examples: (1) a solution of sodium methylate in methyl alcohol is added dropwise to a suspension prepared from benzene, sulphur, and dimethylphosphite, the temperature being kept below 5 DEG C. The residual sulphur is filtered off and the solution added dropwise to a mixture prepared from 2-chloromethyl - 5 - methoxy - 4 - pyrone, sodium iodide and methyl ethyl ketone. The mixture is allowed to stand overnight at room temperature, filtered to remove the salt formed and concentrated under a pressure of 20 to 30 mm. Hg at 40-50 DEG C. to yield a viscous liquid which crystallizes on cooling to yield a solid which is purified by dissolving in boiling benzene and treating with decolourising charcoal to yield the 2 - (0,0 - dimethylthiolophosphorylmethyl)-5-methoxy-4-pyrone; (2) the same product is obtained by reacting sodium 0,0-dimethylthionophosphate with 2-hydroxymethyl-5-methoxy-4-pyrone p-toluene sulphonate in methyl ethyl ketone, the sodium 0,0-dimethylthionophosphate being obtained by adding a solution of sodium methylate in methyl alcohol at about 0 DEG to 5 DEG C. to a suspension of dimethylphosphite, methyl alcohol, and flowers of sulphur, filtering off the residual sulphur and then concentrating the solution at 45 DEG C. under a pressure of 20-30 mm. mercury. The product is effective as a pesticide and systemic insecticide (see Group VI).ALSO:A pesticidal composition comprises the compound 2 - (O, O - dimethylthidophoxylmethyl) - 5 - methoxy - 4 - pyrone of the formula: <FORM:0779449/VI/1> (see Group IV(b)) together with an inert diluent. The diluent may be a solid such as talc or kaolin or the composition may be in the form of an aerosol, emulsion or solution in water or in an organic or aqueous organic medium. The emulsion or solution may contain a wetting agent, dispersing agent or emulsifier of the ionic or non-ionic type and the phosphorus derivative may be formulated as a self-emulsifying concentrate containing the active substance dissolved in the dispersing agent or in a solvent compatible with and containing the dispersing agent, the composition being made ready for use by adding water. Other insecticides including substances having a synergistic effect may be included in the compositions. In examples: (1) the phosphorus derivative is dissolved in a mixture of ethyl alcohol and acetone and a non-ionic emulsifying agent and terpinolene are added followed by the addition of ethyl alcohol to yield a solution containing 10 gm. of active product per 100 cc. which is used after appropriate dilution to combat aphides and red spiders; (2) as in (1) except that the ethyl alcohol is repaced by acetone. The phosphorus derivative is stated to be especially effective as a systemic insecticide and systemic acaricide and examples are given to show its effectiveness as such.