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Process for preparing thiosemicarbazides

A technology of thiosemicarbazide and dithiocarbamic acid, which is applied in the direction of organic chemistry and can solve the problems of not being able to prepare high-quality BTDA

Inactive Publication Date: 2004-08-04
DOW AGROSCIENCES LLC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

MTSC prepared by this method cannot produce high-quality BTDA

Method used

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  • Process for preparing thiosemicarbazides
  • Process for preparing thiosemicarbazides
  • Process for preparing thiosemicarbazides

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0026] Embodiment 1 (DIPEA is excessive 10%)

[0027] Methylamine (77.5 g, 40% solution) and DIPEA (142.2 g) were charged to a 1 liter reactor equipped with a reflux condenser and stirrer. Add CS dropwise with stirring over 30 minutes 2 (76g). Drop CS 2 , the reaction temperature was kept below 30 °C by external cooling. The mixture was stirred for a further 3 hours, then the previous batch of distillate (60 g) was added. The reaction mixture was diluted with water to obtain a 24% DTC (dithiocarbamate) solution.

[0028] Hydrazine hydrate (60.1 g) was added to the DIPEA-DTC mixture. The reaction mixture was heated to 89°C and maintained at 89-92°C under reflux for 2 hours and 20 minutes. The DIPEA was distilled off (the distillation was complete when the temperature was raised above 95° C.), and the reaction mixture was cooled to 15° C. while stirring, whereupon the MTSC crystals separated from the supernatant liquid layer, yielding a yield of isolated MTSC is 73.8%. T...

Embodiment 2

[0029] Embodiment 2 (DIPEA is excessive 30%)

[0030] Methylamine (38.7 g, 40% solution) and DIPEA (82.4 g) were charged to a 0.5 liter reactor equipped with a reflux condenser and stirrer. Add CS dropwise with stirring over 30 minutes 2 (38.1g). Drop CS 2 , the reaction temperature was kept below 30 °C by external cooling. The mixture was stirred for a further 3 hours, then the previous batch of distillate (30 g) was added. The reaction mixture was diluted with water to obtain a 24% DTC (dithiocarbamate) solution.

[0031] Hydrazine hydrate (30.1 g) was added to the DIPEA-DTC mixture. The reaction mixture was heated to 92°C and held at 92°C under reflux for 2 hours and 20 minutes. DIPEA was distilled off (the distillation was complete when the temperature rose to higher than 95° C.), and the reaction mixture was cooled to 15° C. while stirring, so that the MTSC crystals were separated from the clear liquid layer, and the yield of isolated MTSC was 75.8 %.

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Abstract

A process is provided for producing a thiosemicarbazide which includes the steps of reacting an alkylamine with carbon disulphide in the presence of a base selected from N,N-diisopropylethylamine and N,N,-diisopropyl-methylamine to produce an intermediate and converting the intermediate into the thiosemicarbazide. The process has particular application to producing 4-methyl-3-thiosemicarbazide, an intermediate useful in producing the broad-spectrum herbicide tebuthiuron.

Description

Background of the invention [0001] The present invention relates to the method for preparing thiosemicarbazide. [0002] 4-Methyl-3-thiosemicarbazide (MTSC) is an intermediate in the synthesis of 5-tert-butyl-2-methylamino-1,3,4-thiadiazole (BTDA), the parent of the broad-spectrum herbicide buthhiuron body. The chemical name of buthiuron is 1-(5-tert-butyl-1,3,4-thiadiazol-2-yl)-1,3 dimethylurea. [0003] Several synthesises of thiosemicarbazides substituted at the 4-position are described in the literature and roughly summarized as follows: [0004] The reaction of alkyl isothiocyanate and hydrazine, [0005] the reaction of hydrazine with reactive thiocarbamic acid derivatives (acyl chlorides, thiurams monosulfide, etc.), and [0006] • Hydrazinolysis of N-monoalkyl and N,N-dialkyldithiocarbamates. [0007] Currently, the preparation method of MTSC requires the hydrazinolysis of ammonium N-methyldithiocarbamate. It is believed that N-methylammonium dithiocarbamate gene...

Claims

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Application Information

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IPC IPC(8): C07C337/06C07D285/12C07D285/135
CPCC07D285/135C07C337/06
Inventor C·德克勒克
Owner DOW AGROSCIENCES LLC
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