METHOD FOR MAKING THIOBISCARBAMATES

Abstract: A method of preparing a thiobiscarbamate by reacting a nitrogen-containing heterocyclic base and sulfur mono­ chloride or sulfur dichloride, and then reacting the resulting base-sulfur chloride adduct with a carbamate to form a thiobiscarbamate.

Description: METHOD FOR MAKIMG THIOBISCARBAMATES This invention relates to the manufacture of thioblscarbamates having the general formula: EMI1.1 wherein R1 is methyl, ethyl, n-propyl, isopropyl, n-butyl or isobutyl; or the general formula: EMI1.2 wherein R2 is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or CH3S(CH3)2C - and R3 is H or CH2X where X is # # -SCH3-SCH3-, or -SCH3. These biscarbamate compounds O are known to have pesticidal activity. U.S. Patent No. 4004031.discloses a method of making these compounds involving simultaneous reaction of carbamate, base, and sulfur chloride (SCl2 or S2CL2). A disadvantage of this prior art method is its relatively tow yield of products and high production of undesirable biproduces. It is an object of this invention to provide 8 method for making thiobiscarbamate compounds that produces higher yields. It is another object of this invention to provide a method for making thiobiscarbamate compounds that produces less bi-product. These. and other objects are attained by the present invention,one aspect of which comprises: a method for making a compound of the general formula: EMI2.1 wherein R1 is methyl, ethyl, n-propyl, isopropyl, n-butyl or isobutyl comprising the steps of: (a) in presence of solvent, reacting nitrogencontaining heterocyclie base with a sulfur chloride selected from Sic12 or S2C12, or a mixture thereof to form a base-sulfur chloride adduct, and thereafter (b) in presence of solvent, reacting the adduct with acarbamate of the general formula: EMI2.2 wherein R1 is as previously defined. A second aspect of the invention comprises: a method for making a compound of the general formula EMI2.3 wherein R2 is methyl, ethyl, n-propyl, isopropyl, n-butyl, or CH3S(CH3)2C -, and R3 is H or-CH2X wherein X is - SCH3, EMI3.1 <tb> <SEP> 0 <SEP> 0 <tb> <SEP> 11 <SEP> II <tb> - <SEP> S-CH3 <SEP> or <SEP> - <SEP> S <SEP> -CH3, <SEP> comprising <SEP> the <SEP> steps <SEP> of <tb> <SEP> 'I <tb> <SEP> (a)0in <SEP> presence <SEP> of <SEP> solvent <SEP> reacting <tb> a nitrogencontaining heterocyclic base with a sulfur chloride selected from SCl2 or S2C12, or a mixture thereof to formabase-sulfur chloride adduct, and (b) in presence of solvent, reacting the adductwEth a carbamate of the general formula: EMI3.2 wherein R2 and R3 are as previously defined. This invention is predicated on the discovery that complexing nitrogen-containing heterocyc lic base with sulfur chloride in presence of a solvent to form an adduct and thereafter reacting carbamate with the adduct provides a surprising increase in yield. This change in the order of addition of the reactants over that of the prior art is especially effective if the solvent is xylene, and if the sulfur chloride used is SC12. The first step in making thiobiscarbamate compounds in accordance with the present invention is to reactanitrogencontaining heterocyclic base and a sulfur chloride in the presence of a solvent to form a base-sulfur chloride adduct. This .is believed to occur in accordance with the following equation: EMI4.1 base sulfor auduct dichloride or EMI4.2 Base sulfur mono adduct chloride Preferably sufficient base is used so that all of the sulfur chloride is reacted. The preferred bases are pyridine and 2-ethyl-5-methyl pyridine. The most preferred solvents are commercial grade xylene and pyridine. However many solvents are acceptable, including but not -limited to halogenated hydrocarbons such as dichioromethane, chloroform, carbon tetrachloride, tetrachloroethane; ethers such as diethyl ether, tetrahydrofuran, 1,4-dioxane, diisopropyl ether, diphenyl ether, anisole; aromatic solvents such as benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, mesitylene, t-butylbenzene, chlorobenzene, nitrobenzene; and other organic solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, acetonitrile, hexane, cyclohexane and methylcyclohexane. Sulfur chloride is the preferred sulfur chloride. However, this compound decomposes slowly according to the equation EMI4.3 Hence commercial SCl2, which currently is believed to contain roughly 70 to 857. SCl2, is a practical and acceptable sulfur chloride. Sulfur monochloride, S2Cl2, is also acceptable, as are mixtures of SCl2 and S2Cl2 The reaction between the base and the sulfur chloride is preferably carried out for about 0.25 to 1 hour at temperatures between about 10 and 50'C. Nore preferably the reaction temperature is about -10 C to '3000 and the reaction time about 20 min to 60 mien. The second step in the process is to react the adduct withacarbamate in the presence of a solvent. A preferred carbamate is methomyl With pyridine as the base, the reaction between methomyl and basesulfur dichloride adduct is believed to proceed EMI5.1 <tb> as <SEP> follows: <tb> <SEP> C,, <SEP> \II <tb> ri <SEP> + <SEP> "\\'N&num; <tb> <SEP> tCH3 <SEP> Na <SEP> S <SEP> N <tb> <SEP> ci <SEP> C1 <tb> <SEP> Adduct <tb> <SEP> methomyl <tb> <SEP> I <tb> <SEP> (CH3-C <SEP> ¯ <SEP> N-O-C-N <SEP> + <SEP> S <SEP> + <SEP> 2 <SEP> )) <tb> <SEP> Ir <SEP> I1 <SEP> h) <tb> <SEP> a <SEP> preferred <SEP> thiobiscarbamate <SEP> H <SEP> Cl <tb> The solvents acceptable for the first step in the process, the adduct forming step, are also acceptable for the second step, the reaction with carbamate. The preferred solvents for the second step are again pyridine and xylene, but other solvents are acceptable. Since the first step yields an adduct-solvent mixture., preferably'the second step is perfomed by adding carbamate to the adduct-solvent mixture resulting from the first step. Of course, the adduct could be separated from the solvent used for the first step and a different solvent used for the second step, but such extra processing is not necessary. The second step is preferably carried out at a temperature of from about 0 C to 45"C, more preferably about 15"C to 320C, and for a reacton time of about 1 hour to 96 hours, more preferably about 1 hour to 20 hours. When pyridine is used as both solvent and base, purification of the product mixture from the second step is preferably effected by washing and/or slurrying with water or a C-lto C-5 alcohol. EXAMPLES Examples 1 to 12 illustrate the present invention and examples 13 to 28 illustrate the prior art method. All experiments were conducted under a nitrogen atmosphere in a 500 ml, four-necked flask equipped with a thermometer, a mechanical stirrer, a drying tube, and a pressure-equalizing addition funnel attached to a nitrogen inlet tube. The assembled apparatus was dried with a heat gun under a nitrogen atmosphere prior to the experiments. PROCEDt'RE FOR EYMaYPLES 1 to 10 The first step was performed as follows: The adduct was formed by preparing a solution of 28.5 g. pyridine and 200 g. solvent at about 2 C. Sulfur chloride in the amount of 20.74 grams was added to the solution dropwise over a 15 minute period while maintaining temperature of 2-4"C. The adduct precipitated. The adduct-solvent mixture was stirred for 30 minutes The second step in the process was performed as follows: Methomyl in the amount of 53.53 g was added to the mixtures and the temperature was allowed to rise to the reaction temperature. This temperature was maintained fdr the reaction time while stirring. The reaction mixture was filtered and cake washed twice with a 150 g of fresh solvent. The filtered cake was then washed four times with 150 g of water at 40 C. The cake was dried and analyzed for purity of the thiobiscar- bamate compound. The yield was calculated multiplying the weight of the dried filter cake by the purity in weight 7. and dividing by the theoritical yield of the biscarbamate compound. The results appear in Table 1. PROCEDURE FOR EXAMPLES 11 and 12 These experiments were preformed the same as example 1 to 10 except as noted in foot notes c and d in Table 1. TABLE I - EXAMPLES USING THE PRESENT INVENTION 2ND STEP 2ND STEP DRIED SULFURa REACTION REACTION CAKE %ABS* EXAMPLE SOLVENT CHLORIDE TIME(HR) TEMP( C) WT.(g) PURITY YIELD 1 Toluene SCl2 4 30 32.75 97.5 64.9 2 Toluene SCl2 5 30 37.04 96.5 62.8 3 Toluene SCl2 16 35 37.24 98.7 62.8 4 Xyleneb SCl2 5 25 34.08 98.4 76.6 5 Xyleneb SCl2 11 25 37.87 94.0 81.3 6 Xyleneb SCl2 20 25 55.45 96.3 91.3 7 CH2Cl2 SCl2 2 25 30.61 93.6 49.0 8 CH2Cl2 SCl2 4 25 31.27 94.7 50.7 9 Ethylbenzene SCl2 20 25 30.87 95.3 50.3 10 Ethyl ether SCl2 20 25 46.63 89.5 71.4 11c Toluene S2Cl2 16 40 44.60 98.2 74.9 12d Xylene SCl2 66 25 48.96 90.2 75.5 aCommercial grade SCl2 belived to be about #85% SCl2 by wt. bCommercial grade mixed xylene containing about 19% 0,42% m, 18% p xylene and 21% ethylbenzene. cSulfur monochloride (21.13 g) was added to a solution of 27.10 g of pyridine in 250 ml of toluene at 25-30 C. After 15 minutes, 53.53 g of methomyl was added at once and then heated to 40 C for 16 hours. After filtration, toluene washing and water washing, the product was vacuum dried to give 44.60g of product. d2-Ethyl-5-methylpyridine (46.3 g) was substitued for pyridine. Procedure for Examples 13 to 28 A suspension of 50 g methyl, 25 g base, and 300 ml solvent was prepared and warmed to the reaction temperature. To the suspension was added 16.5 g sulfur chloride dissolved in 20 ml solvent. The reaction temperature was maintained for the reaction time listed in the table. The resulting slurry was filtered and the cake washed with 300 ml of cold water twice, and then triturated twice with 300 ml methanol and filtered. The solid was vacuum dried at 45 C for 2 hours. The results are listed in Table II. The yield was calculated the same way it was for Examples 1 to 12. Variations to the above procedure for certain examples are described in the foot note to Table II. TABLE II - EXAMPLE USING PRIOR ART METHOD WT. OF SULFUR REACTION REACTION PRODUCT PURITY % AUS* EXAMPLE SOLVENT CHLORIDE BASE TIME(HR) TEMP( C) (g) (DY LC) YIELD 13 CH2Cl2 SCl2 pyridine 16 -10 to 25 22.40 90.9 37.1 14 Toluene SCl2 pyridine 48 20 to 28 40.99 97.4 70.4 15a CH2CN SCl2 pyridine 16 25 to 35 2.96 94.9 4.9 16 Hexane SCl2 pyridine 16 25 to 40 27.08 91.5 43.7 17 p-Xylene SCl2 pyridine 16 20 to 30 41.55 96.4 70.7 18 Pyridine SCl2 pyridine 19 20 to 30 41.27 93.5 68.1 19a DMF SCl2 pyridine 20 0 to 10 37.25 92.1 60.5 20 0-Xylene SCl2 pyridine 18,5 20 to 30 39.09 89.1 60.9 21 Ethylbenzene SCl2 pyridine 4 30 29.34 94.1 47.0 22 Xylenes SCl2 pyridine 4 30 38.03 87.5 56.9 23 Toluene SCl2 TEAc 19 21 13.88 82.3 15.3 24 p-Xylene SCl2 quinolined 2 25 32.64 64.3 37.0 25 Cyclohexane SCl2 methylethyl-e 1 30 27.24 85.4 41.0 pyridine 26 Toluene SCl2 (soquinolinef 16 35 38.07 85.36 57.29 27 CH2Cl2 S2Cl2 pyridine 18 35 33.68 89.0 64.5 20b TMF/Benzene S2Cl2 pyridine 10 0 7.00 95.2 18.9 aSCl2 was added without solvent dlution. bDone exactly as described in U.S. 4,004.031 (Ciba-Geiby) issued January 18, 1977. cTriethylamine (36 g) was substitued for the pyridine. dQuinoline (40.8 g) was substitued for the pyridine. eMethylethylpyridine (40.81 g) was substitued for the pyridine. fIsoquinoline (40,81 g) was substitued for the pyridine. The superiority of the present invention can readily be seen by comparing examples 4, 5 and 6 wherein yields of 76.6, 81.3 and 91.3% were attained, with prior art examples 17, 20 and 22 wherein yields of only 70.7, 60.9 and 56.9 were attained using the same or similar solvent and the same base. Further evidence of the present methods superiority can be ascertained by comparing examples 7 and 8 (49.0 and 50.7% yields) with prior art example 13 wherein only 37.1% yield was attained using CH2C12 as the solvent, and pyridine as the base in both methods. Example 11 shows that good yields (here 74.9%) can be attained by the present invention using S2C12. Likewise, example 12 shows that the present invention can achieve a good yield with 2-ethyl-5-methyl pyridine as the base. Example 29 - Reaction Using Pyridine as Both Solvent and Base The first step was performed as follows: The adduct was formed by adding 23 grams of sulfur dichloride to 90 grams of pyridine dropwise over a period of about 15 minutes at 50C. The adduct precipitated to form an adduct slurry. The second step was performed as follows: Into Åa separate reactor was placed 53.5 grams of methomyl and 60 grams of pyridine. The resulting mixture was stirred until the methomyl dissolved, The solution was maintained at a temperature of 200C to 250C, The adduct slurry was pumped into the methomyl (pyridine solution with stirring while maintaining a reaction temperature of 209C to 25 C. Adduct addition was completed after about 1 hour. A reaction temperature of 20"C to 2500 was maintained for an additional four hours for the resulting mixture. Purification of product was effected as follows: 300 grams of methanol was added to the above mixture to form a slurry. The slurry was then cooled to -50C with stirring. The slurry was filtered to form a filter cake. The filter cake was washed with 150 grams of methanol at -50C. The filter cake was then re-slurried in 150 grams of methanol at -5 C. The re-slurry was filtered and then washed twice with 150 grams of methanol at -50C. The cake was dried in a vacuum oven at 400C and 40 mm Hg. pressure. The cake consisted of 50.0 grams of product having a melting point of 1690C to 1700C.

Claims: CLAIMS: 1. A method for making a compound of the general formula: EMI13.1 wherein R1 is methyl, ethyl, n-propyl, isopropyl, n-butyl or isobutyl comprising the steps of: (a) reacting pyridine with a sulfur chloride selected from SC12 or S2C12, or a mixture thereof to form a pyridine-sulfur chloride adduct, in the presence of excess pyridine, and (b) reacting the adduct with a carbamate of the general formula: EMI13.2 wherein R1 is as previously defined, in the presence of pyridine. 2. A process as claimed in claim 1 which further comprises the step of: (c) purifying the product of step (b) by washing or slurrying the product at least once with water or a C-l to C-S alcohol.

Inventors: ASHWORTH, ROBERT WILLIAM, FU, WALLACE YAM-TAK
Applicants: UNION CARBIDE CORPORATION
Application year: 1981
Main classification: C07C148