Process for the preparation of phenyl (1,3,5-triazin-2-yl) carbamates

Abstract: The present invention discloses a process for the preparation of phenyl (1,3,5-triazin-2-yl)carbamates of the formula (I) wherein R¹ is hydrogen atom, C₁-C₄ alkyl or C₁-C₄ alkoxy R² and R³ are independently hydrogen atom, halogen atom, C₁-C₄ alkyl, C₁-C₄ alkoxy, C₁-C₄ alkylthio, C₁-C₄ haloalkyl, C₁-C₄ haloalkoxy, C₁-C₄ haloalkylthio, C₂-C₄ alkoxyalkyl or NR⁷R⁸ R⁷ and R⁸ are independently hydrogen atom or C₁-C₄ alkyl R⁴, R⁵ and R⁶ are independently hydrogen atom, halogen atom, C₁-C₄ alkyl or C₁-C₄ alkoxy which comprises: reacting 2-amino-1,3,5-triazines of the formula (II) with diphenyl carbonates of the formula (III) in the presence of alkali metal hydrides in aprotic polar solvents.

Description: BACKGROUND OF THE INVENTION This invention relates to a process for the preparation of phenyl (1,3,5-triazin-2-yl)carbamates which are useful intermediates for producing of herbicidally active sulfonylurea compounds. EP-A-85028(corresponding to JP-A-58146572), EP-A-103543(corresponding to JP-A-5973583), JP-A-60139691 and EP-A-238070(corresponding to JP-A-6438091) disclose that phenyl (1,3,5-triazin-2-yl)carbamates and phenyl (pyrimidin-2-yl)carbamates are used as intermediates for producing of herbicidally active sulfonylurea compounds. The preparations of phenyl (pyrimidin-2-yl)carbamates are relatively simple methods and have a good yield. However, a simple synthesis method of phenyl (1,3,5-triazin-2-yl)carbamates is not reported. (c.f. reference examples 53 and 57 in EP-A-238070) SUMMARY OF THE INVENTION An object of the present invention is to provide a process to prepare phenyl (1,3,5-triazin-2-yl)carbamates of the formula (I) as shown below, which is simple and has a good yield: wherein R 1 is hydrogen atom, C 1 -C 4 alkyl or C 1 -C 4 alkoxy R 2 and R 3 are independently a hydrogen atom, halogen atom, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, C 1 -C 4 alkylthio, C 1 -C 4 haloalkyl, C 1 -C 4 haloalkoxy, C 1 -C 4 haloalkylthio, C 2 -C 4 alkoxyalkyl or NR 7 R 8 R 7 and R 8 are independently a hydrogen atom or C 1 -C 4 alkyl R 4 , R 5 and R 6 are independently a hydrogen atom, halogen atom, C 1 -C 4 alkyl or C 1 -C 4 alkoxy DETAILED DESCRIPTION OF THE INVENTION According to the present invention there is therefore provided a process for the preparation of a phenyl (1,3,5-triazin 2-yl)carbamate of the formula (I) wherein R 1 is a hydrogen atom, C 1 -C 4 alkyl or C 1 -C 4 alkoxy, R 2 and R 3 are independently a hydrogen atom, halogen atom, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, C 1 -C 4 alkylthio, C 1 -C 4 haloalkyl, C 1 -C 4 haloalkoxy, C 1 -C 4 haloalkylthio, C 2 -C 4 alkoxyalkyl or NR 7 R 8 , R 7 and R 8 are independently a hydrogen atom or C 1 -C 4 alkyl, R 4 , R 5 and R 6 are independently a hydrogen atom, halogen atom, C 1 -C 4 alkyl or C 1 -C 4 alkoxy, which process comprises : reacting a 2-amino-1,3,5-triazine of the formula (II) in an aprotic polar solvent, with a diphenyl carbonate of the formula (III) characterized in that (i) said 2-amino-1,3,5-triazine is reacted with an alkali metal hydride (ii) said aprotic polar solvent is N,N-dimethylacetamide or N-methylpyrrolidone, and (iii) the addition of the diphenyl carbonate of the formula (III) is effected after evolution of hydrogen gas in step (i), or characterized in that (vi) said diphenyl carbonate is reacted with an alkali metal salt of said 2-amino-1,3,5-triazine, and (v) said aprotic polar solvent is N,N-dimethylacetamide or N-methylpyrrolidone. Halogen in the above definitions, and also as a moiety of haloalkyl, haloalkoxy and haloalkylthio, is fluorine, chlorine, bromine and iodine, with fluorine and chlorine being preferred. Haloalkyl, haloalkoxy and haloalkylthio are substituted with one or more halogen atoms. In suitable 2-amino-1,3,5-triazines of the formula (II), R 1 is a hydrogen atom, R 2 and R 3 are independently C 1 -C 2 alkyl, C 1 -C 2 alkoxy, C 1 -C 2 fluoroalkyl, C 1 -C 2 fluoroalkoxy, C 2 -C 4 alkoxyalkyl or NR 7 R 8 , R 7 and R 8 are independently a hydrogen atom or C 1 -C 2 alkyl. Fluoroalkyl, fluoroalkoxy and fluoroalkylthio in the above definitions are substituted with one or more fluorine atoms. In suitable diphenyl carbonates of the formula (III), R 4 , R 5 and R 6 are independently a hydrogen atom or methyl. The process of the invention is illustrated by the following reaction scheme, wherein R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are as defined above and M is an alkali metal atom. As suitable alkali metal hydrides, sodium hydride or potassium hydride may be used. The reaction is preferably carried out at a temperature from 0 to 40 °C to give phenyl (1,3,5-triazin-2-yl)carbamates of the formula (I) in good yields. The reaction temperature may be out of the range from 0 to 40 °C, if necessary and if it does not give the product in bad yields. The reaction time is preferably 5-30 minutes after mixing 2-amino-1,3,5-triazines of the formula (II), alkali metal hydrides and diphenyl carbonates of the formula (III). But, elongation of the reaction time is allowed if it does not affect the reaction yield. Alkali metal hydrides and diphenyl carbonates of the formula (III) are employed an equimolar amount per mole of 2-amino-1,3,5-triazines of the formula (II), respectively, to give the objective compound in good yields. But, per mole of the most expensive starting compound, excesses of the other starting compounds may be used if this does not affect the reaction yield. The used amount of a reaction solvent is not restricted especially, since the object of the invention is achieved once the starting materials are mixed well in it. The ratio of the sum of used starting materials (gr. weight) to used solvent (ml. volume) is preferably in the range of 1/3 - 1/10 (gr/ml). In the case of isolating phenyl (1,3,5-triazine-2-yl)carbamates of the formula (I) from the resultant mixture of above reaction operation, the resultant mixture is poured into the iced-water containing 1.1 - 5 moles of hydrogen chloride per mole of used alkali metal hydride. The precipitate is filtered off and washed with petroleum ether or hexane to give the product. Of course, if necessary, recrystallization or column chromatography may be used for further purification process. However, in the case of using phenyl (1,3,5-triazin-2-yl)carbamates of the formula (I) for the reagent of [(1,3,5-triazin-2-yl)amino]carbonylation at the nitrogen atom of a sulfonamide group, the aprotic polar solvent containing phenyl (1,3,5-triazin-2-yl)carbamates of the formula (I) and alkali metal phenoxides of the formula (IV) (corresponding to the above resultant reaction mixture) may be used without further adding base compounds. Therefore, the use of the above resultant reaction mixture is of commercial interest on account of the advantages mentioned. The invention is further illustrated by the following examples, in which 2-amino-4,6-dimethoxy-1,3,5-triazine as 2-amino-1,3,5-triazines of the formula (II), diphenyl carbonate as diphenyl carbonates of the formula (III), sodium hydride as alkali metal hydrides, N,N-dimethylacetamide as aprotic polar solvents and methyl 2-(aminosulfonyl)benzoate as compounds having a sulfonamide group are used. Example 1 The preparation of phenyl (4,6-dimethoxy-1,3,5-triazin-2-yl)carbamate Into 50 ml Erlenmeyer flask, were added 2-amino-4,6-dimethoxy-1,3,5-triazine 2.00 g (0.0128 mole) and dry N,N-dimethylacetamide 18 ml and stirred in the suspended condition. To the suspended mixture, at the room temperature, was added 60 % oily sodium hydride 0.51 g (0.0128 mole) (equal to the preparation of sodium salt of 2-amino-4,6-dimethoxy-1,3,5-triazine). The reaction mixture was homogeneous after vigorous evolution of hydrogen gas. A solution of diphenyl carbonate 2.74 g (0.0128 mole) and dry N,N-dimethylacetamide was subsequently added to the mixture under the water cooling during 10 minutes, and stirred for further 10 minutes. The reaction mixture was poured into 20 ml iced water containing 1.4 ml hydrogen chloride (35 % aq soln). The precipitate was filtered off and wash with iced water and then petroleum ether. After being air-dried, the product was obtained. The obtained amount (yield of theory) and the physical property were showed hereinafter. 2.60 g (73.5 % of theory) mp.141-142 °C IR(KBr,cm -1 ) 3304, 1780, 1752, 1618, 1482 1390, 1360, 1290, 1192 NMR(CDCl 3 , δ) 4.0(6H,s,OCH 3 × 2 ) 7.05 - 7.51(5H, m, Aromatic H) 8.28 - 8.7(1H,bs,NH) Example 2 The use of the N,N-dimethylacetamide mixture for [(1,3,5-triazin-2-yl)amino]carbonylation at the nitrogen atom of a sulfonamide group [1] Preparation of the N,N-dimethylacetamide mixture containing phenyl (4,6-dimethoxy-1,3,5-triazin-2-yl)carbamate and sodium phenoxide Into 50 ml Erlenmeyer flask, were added 2-amino-4,6-dimethoxy-1,3,5-triazine 1.00 g and dry N,N-dimethylacetamide 9 ml, and stirred in suspended condition. To the suspended mixture, at the room temperature, was added 60 % oily sodium hydride 0.26 g (equal to the preparation of sodium salt of 2-amino-4,6-dimethoxy-1,3,5-triazine). The reaction mixture was homogeneous after vigorous evolution of hydrogen gas. A solution of diphenyl carbonate 1.37 g and dry N,N-dimethylacetamide 4.2 ml was subsequently added dropwise to the mixture under water cooling during 6 minutes. Stirring was maintained for further 10 minutes to prepare the N,N-dimethylacetamide mixture containing phenyl (4,6-dimethoxy-1,3,5-triazin-2-yl)carbamate and sodium phenoxide. [2] Preparation of methyl 2-[[(4,6-dimethoxy-1,3,5-triazin-2-yl)aminocarbonyl]aminosulfonyl]benzoate The N,N-dimethylacetamide mixture in 50 ml Erlenmeyer flask, obtained in [1], was stirred under iced water cooling. To the mixture, was added dropwise a solution of methyl 2-(aminosulfonyl)benzoate 1.25 g and N,N-dimethylacetamide 3 ml for 5 minutes. The mixture was stirred for further 1.5 hours. The mixture was subsequently poured into 130 ml iced water containing 0.7 ml hydrogen chloride (35 % aq soln). A white precipitate was filtered off and washed with iced water and then petroleum ether, and air-dried to give the product. The obtained amount (yield of theory) and the physical property were showed hereinafter. 1.90 g (82.2 % of theory) purity by HPLC 97.8 % mp.171-173 °C IR (KBr,cm -1 ) 3320, 1742, 1608, 1494, 1388, 1292 NMR (d 6 -DMSO , δ) 3.8(3H, s) 3.95(6H, s) 7.26 - 8.3 (5H, m) 10.9(1H, bs)

Claims: A process for the preparation of a phenyl (1,3,5-triazin 2-yl)carbamate of the formula (I) wherein R 1 is a hydrogen atom, C 1 -C 4 alkyl or C 1 -C 4 alkoxy, R 2 and R 3 are independently a hydrogen atom, halogen atom, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, C 1 -C 4 alkylthio, C 1 -C 4 haloalkyl, C 1 -C 4 haloalkoxy, C 1 -C 4 haloalkylthio, C 2 -C 4 alkoxyalkyl or NR 7 R 8 , R 7 and R 8 are independently a hydrogen atom or C 1 -C 4 alkyl, R 4 , R 5 and R 6 are independently a hydrogen atom, halogen atom, C 1 -C 4 alkyl or C 1 -C 4 alkoxy, which process comprises: reacting a 2-amino-1,3,5-triazine of the formula (II) in an aprotic polar solvent, with a diphenyl carbonate of the formula (III) characterized in that (i) said 2-amino-1,3,5-triazine is reacted with an alkali metal hydride (ii) said aprotic polar solvent is N,N-dimethylacetamide or N-methylpyrrolidone, and (iii) the addition of the diphenyl carbonate of the formula (III) is effected after evolution of hydrogen gas in step (i). A process for the preparation of a phenyl (1,3,5-triazin 2-yl)carbamate of the formula (I) wherein R 1 is a hydrogen atom, C 1 -C 4 alkyl or C 1 -C 4 alkoxy, R 2 and R 3 are independently a hydrogen atom, halogen atom, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, C 1 -C 4 alkylthio, C 1 -C 4 haloalkyl, C 1 -C 4 haloalkoxy, C 1 -C 4 haloalkylthio, C 2 -C 4 alkoxyalkyl or NR 7 R 8 , R 7 and R 8 are independently a hydrogen atom or C 1 -C 4 alkyl, R 4 , R 5 and R 6 are independently a hydrogen atom, halogen atom, C 1 -C 4 alkyl or C 1 -C 4 alkoxy; which process comprises: reacting a 2-amino-1,3,5-triazine of the formula (II) in an aprotic polar solvent, with a diphenyl carbonate of the formula (III) characterized in that (vi) said diphenyl carbonate is reacted with an alkali metal salt of said 2-amino-1,3,5-triazine, and (v) said aprotic polar solvent is N,N-dimethylacetamide or N-methylpyrrolidone.

Inventors: ARABORI HIDEO, KANDA YOICHI, ARABORI, HIDEO, KANDA, YOICHI
Applicants: KUREHA CHEMICAL IND CO LTD, KUREHA KAGAKU KOGYO KABUSHIKI KAISHA
Application year: 1993
Main classification: C07D251
IPC codes: C07D251