IL42442A - Preparation of thiohydroximate carbamates - Google Patents

Claims (3)

1. WE CLAIM: 1. In the method of making S-alkyl thlohydroxlmate carbamates of the formula: 0 II R-C=NOCNHCH3 I I SR1 wherein R is methyl, ethyl, or ; is methyl, ethyl, n-propyl, or isopropyl; R2 is hydrogen, methyl, ethyl, n-propyl, or isopropylj and R3 is hydrogen or methyl, provided that when R2 is ethyl, n-propyl or isopropyl, R3 is hydrogen; by reacting methyl isocyanate with an S-alkyl thiohydroximate of the formula: R-C=NOH * II SR]_ wherein R and R-L are as defined above, the improvement which comprises carrying out the reaction by adding the methyl isocyanate, in gaseous or liquid form, to an agitated bed of solid particles of the thiohydroximate in the absence of a continuous liquid phase while removing the heat of reaction, the rates of isocyanate addition and heat removal being balanced so as to maintain the temperature of the reaction mass at or above 0°C. but below the melting points of the thiohydroximate starting material and the thiohydro imate carbamate product.

2. Process of claim 1 wherein the rate of isocyanate addition and heat removal are balanced so as to maintain the temperature of the reaction mass at or above 25°C but below the temperature at which the reaction mass becomes tacky.

3. Process of claim 2 wherein the rates of isocyanate addition and heat removal are balanced such that the reaction mass resembles a damp powder throughout the period of isocyanate addition. Process of claim 1 wherein at least one solid particulate inert diluent or a heel of thiohydroxlmate carbamate is mixed with the thiohydroxlmate particles before or during the reaction. 5. Process of claim 1 wherein at least one solid particulate inert diluent and a heel of the thiohydroxlmate carbamate are mixed with the thiohydroxlmate before or during the reaction. 6. Process of claim 1 wherein the mole ratio of isocyanate to thiohydroxlmate is in the range of 0.95 to 1.05. 7. Process of claim 1 wherein the mole ratio, of isocyanate to thiohydroxlmate is in the range of Ο.98 to 1.02. 8. Process of claim 6 wherein a catalytic amount of a tertiary amine or alkali metal hydroxide is present in the reaction mass . 9. Process of claim 8 wherein R is «■ N-°C- and R3 ¾ j R2 j and R3 are methyl. 10. Process of claim 6 wherein R and are both methyl. 11. In the method of making S-methyl N- [methyl-carbamoyl)oxy_7thioacetimidate by reacting methyl isocyanate with S-methyl N-hydroxythioacetimidate in the absence of solvent, the improvement which comprises contacting the reactants under conditions such that for at least a terminal portion of the reaction^ the reaction mass is maintained as a continuous liquid phase. 12. Method of claim 11 wherein the reaction mass is maintained as a continuous liquid phase for at least the terminal five percent of the reaction. 15. Method of claim 11 wherein the reaction mass is maintained as a continuous liquid phase for at least the terminal 25$ of the reaction. l . Method of claim 11 wherein the rates of re-actant addition and heat removal are balanced such that at the completion of the reaction the temperature of the reaction mass is between about 75° and 85°C. 15· Method of claim 11 wherein the methyl isocyanate is contacted with solid S-methyl N-hydroxythioacetimidate, and further wherein the temperature of the reaction mass is permitted to rise autogeneously at the beginning of the reaction until said reaction mass becomes a continuous liquid phase, and the reaction mass is maintained as a continuous liquid phase for the remainder of the reaction. 16. Method of claim 15 wherein gaseous methyl-isocyanate is contacted with said solid S-methyl N-hydroxythioacetimidate . 17. Method of claim 11 wherein diluent or S-methyl N-^methylcarbamoyl)ox_7thioacetimidate heel is mixed with at least one of the reactants before or during the reaction. 18. Method of claim 11 wherein the molar ratio of Isocyanate to thioacetimidate is approximately Ο.9.5 to I.05. 19. Process of claim 11 wherein a catalytic amount of a tertiary amine or alkali metal hydroxide is present in the reaction mass. 20. Method of claim 11 further comprising cooling the reaction product sufficiently to cojvert it from the molten state to a crystalline solid state, and thereafter further cooling the crystalline solids to approximately 35° to oeC.