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Process for the preparation of thiamethoxam

A technology for thiamethoxam and its use, applied in the field of 3--5-methyl-1, capable of solving problems such as unsatisfactory yield and purity level

Inactive Publication Date: 2020-06-19
JIANGSU ROTAM CHEM
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the yield and purity level are unsatisfactory

Method used

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  • Process for the preparation of thiamethoxam
  • Process for the preparation of thiamethoxam
  • Process for the preparation of thiamethoxam

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0079] Embodiment 1: the synthesis of thiamethoxam

[0080] 1.1 Preparation of 3,6-dihydro-3-methyl-N-nitro-2H-1,3,5,oxadiazin-4-amine

[0081] 3,6-Dihydro-3-methyl-N-nitro-2H-1,3,5,oxadiazin-4-amine was prepared using the following reaction scheme:

[0082]

[0083]100 kg of N-methyl-nitroguanidine and 64 kg of paraformaldehyde were charged into a 1000 L reactor. 350 kg of acetic acid were added, after which the resulting mixture was heated to 70° C. and kept at this temperature for 6 hours. Thereafter, the solvent (acetic acid) was removed by distillation under vacuum. 175 kg of 10% aqueous NaOH were added with stirring, after which the resulting mixture was cooled and stirred for 30 minutes. The resulting mixture was discharged into a centrifuge for separation. The resulting cake was dried using a Biconical dryer to obtain 98 kg of 3-methyl-N-nitro-1,3,5,oxadiazine-4-imine (purity 97%, Yield 71.5%).

[0084] 1.2 Preparation of 2-chloro-allylthioisocyanide

[0...

Embodiment 2

[0096] Example 2: Preparation of Crystalline Thiamethoxam Using Methanol

[0097] 2 g of thiamethoxam prepared as in Example 1 were heated in 10 g of methanol until complete dissolution was achieved. The resulting solution was heated at reflux for 30 to 60 minutes, then cooled to room temperature. The resulting mixture was filtered to separate solids. The resulting solid was washed several times with methanol and dried under high vacuum to give technical grade pure thiamethoxam crystals (purity: 98%).

[0098] The crystals were characterized as thiamethoxam polymorph A using both infrared (IR) spectroscopy and X-ray diffraction.

[0099] Form A thiamethoxam has figure 1 The X-ray powder diffraction pattern shown, where the reflections are listed in Table 1 below.

[0100] Table 1

[0101]

[0102] The IR spectrum of Form A thiamethoxam is listed in figure 2 middle. The IR spectra exhibited at 2933.62, 2161.78 and 1593.88cm -1 characteristic peaks at .

Embodiment 3

[0103] Example 3: Preparation of Crystalline Thiamethoxam Using Xylene

[0104] 2 g of thiamethoxam prepared as described in Example 1 was dissolved in 10 g of xylene while applying low heat on a hot plate. The resulting mixture was heated at reflux for 30 to 60 minutes and then cooled to room temperature. The resulting mixture was filtered to separate solids. After filtration, the solid was washed several times with xylene and dried under high vacuum to give technical grade pure thiamethoxam crystals (purity: 97%).

[0105] The crystals were characterized as Thiamethoxam Form A using infrared spectroscopy and X-ray diffraction as described in Example 2.

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Abstract

There is disclosed the use of a solvent system comprising a C1 to C4 alcohol, a substituted benzene derivative bearing two or more C1 to C4 alkyl substituents, or a mixture thereof in the preparationof a crystalline form of 3-(2-chloro-1, 3-thiazol-5-yl methyl)-5-methyl-1, 3, 5-oxadiazinan-4-yledene (nitro) amine (thiamethoxam). Crystalline thiamethoxam prepared in this way exhibits a significantly improved stability, in particular a resistance to photolysis, compared with crystalline thiamethoxam prepared using other solvents.

Description

[0001] Cross References to Related Applications [0002] This application claims priority from European Patent Application No. 17199710.9 filed on November 2, 2017, the content of which is hereby incorporated by reference in its entirety. technical field [0003] The present invention relates to 3-(2-chloro-1,3-thiazol-5-ylmethyl)-5-methyl-1,3,5-oxadiazin-4-ylidene (nitro)amine (clothiazolin oxazine) preparation. Background technique [0004] 3-(2-Chloro-1,3-thiazol-5-ylmethyl)-5-methyl-1,3,5-oxadiazin-4-ylidene(nitro)amine (under the common name Clothiazole Zines are known) are widely used commercial agrochemicals exhibiting insecticidal activity. Thiamethoxam and a process for its preparation were first disclosed in EP 0 580 553 . [0005] Thiamethoxam was first marketed in 1991 and is a systemic insecticide that is rapidly absorbed by plants and transported to all parts of the plant, where it acts as a deterrent to insect feeding. Thiamethoxam is active in the stomac...

Claims

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Application Information

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IPC IPC(8): C07D417/06A01N51/00A01P7/04
CPCC07D417/06
Inventor 詹姆斯·蒂莫西·布里斯托
Owner JIANGSU ROTAM CHEM
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