SU773043A1 - Method of preparing 2-nitro-3,6-diaminopyridines - Google Patents

Description

This invention relates to a process for the preparation of 6-substituted 2-nitro-3-amino-pyridine in the general formula 1,. where -R Zhg, ShSNz, (01Gz) 2, T HCgHs Н (С2Н5) 2 ,, О СЛ О which can serve as starting materials for the synthesis of biologically active substances. A method of producing 2-nigro-3; 6-diaminopyridines is known by boiling mixtures of 2-nitro-3-azicopyridine with amines in water for 1 hour. However, preparatively, with yields of no more than 4%, it is possible to isolate only products, O. In other cases, compounds 1 were isolated by preparative chromatography on plates, since the reaction yields a mixture of 3-4 substances with close Rs. This method cannot be proposed as a method for obtaining compounds of the above formula, but is of theoretical interest only. The purpose of the invention is to increase the yield of target products. This goal is achieved by boiling an aqueous solution of 2-nitro-3-azido-pyridine, usually 4–5 hours, further cooling the solution to 18–26 ° C and adding 1–1.5 fold molar amount of amine. The yields of 2-nitro-3,6-diaminopyridines are 40-50%. The proposed method can quantitatively produce 2-nitro-Z-aminopyridines substituted in the 6 position, which were previously determined only by chromatography. The target products are obtained without impurities, in crystalline form. They can

but used for further syntheses without further purification.

The increase in the yields of the final products and the ease of their isolation from the reaction mass is due to the fact that 2-nitro-3-azidopyridine, when boiling its aqueous solution for several hours, turns into pyrido (2,3-c) furoxane, which reacts with amines at room temperature to form 2-nitro-3,6-diaminoprecidine with yields of 70-85%.

Example 1, 2-Nitro-3-azidopyridine. A solution of 1.2 g (0.17 mmol) of sodium nitrite in 4 ml of water is added dropwise to a solution of 2 g (0.14 mmol) of 2-nitro-3-aminopyridine in 35 ml of 5O% sulfuric acid. To the diazo solution add

an aqueous solution of 1.2 g (0.2 tmol) of sodium azide. With strong foaming, a colorless crystalline precipitate almost immediately falls out. The yield of 1.8 g (78.5%). T. pl. 40-42 C (needles, out of water).

Example 2. 2-Nitro-3,6-diaminopyriain. 2 g (0.12 mmol) of 2-nitro-3-azidopyridine are boiled in 30 ml of water for 4-5 hours. The reaction solution is cleaned with charcoal and filtered. To warm masterbatch

at a solution of 26 ° C, a 1-1.5 fold molar excess of amine is added. The reaction mass immediately turns red, a precipitate is formed, which is left at room temperature.

temperature for 1 h. Then the red crystalline precipitate is filtered off.

The characteristics of the compounds obtained are listed in the table.

Claims (1)

Claim The method of obtaining 2-nitro-3,6-diaminopyricines of the formula jCT> where K = NH ₂ , NHCH ₃ , N (CH ₃ ) _Z , NHC ₂ H _{5> 50} N (C ₂ H ₅ ) ₂ BHCzfHs by the interaction of 2-nitro-3-azizopyridine with the corresponding amine in an aqueous medium, characterized in that, in order to increase the yield of the target product, an aqueous solution of 2-nitro-3-azidopyridine is boiled, cooled to a temperature of 18-26 ° C and add 1-1.5 times the molar amount of amine.