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Method for preparing 2-quinoxalinol
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A technology of quinoxaline alcohol and general formula, which is applied in the field of compound preparation, can solve the problems of high production cost, high price of reducing agent, excessive reduction, etc., and achieve the effects of reducing production cost, benefiting environmental protection, and less by-products
Inactive Publication Date: 2012-11-28
ZHEJIANG HETIAN CHEM CO LTD +1
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Problems solved by technology
[0007] The price of the reducing agent used in the above method is relatively high, and the production cost of the product is large.
Using hydrogen as a reducing agent, an explosion may occur through low-pressure catalytic hydrogenation, which poses a great safety hazard, and there is also the possibility of over-reduction, resulting in a large amount of over-reduction by-products
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Embodiment 1
[0021] Step (1): Synthesis of 6-chloro-2-hydroxyquinoxaline-4-oxide
[0022] Add 30g of p-chloro-o-nitroacetoacetanilide (95%) into 10% aqueous sodium hydroxide solution (the amount of sodium hydroxide is 40g), raise the temperature to 70°C, stir and react for 2 hours, add 400ml of water, filter, Unreacted solid material was filtered off. The filtrate was acidified with hydrochloric acid, and a solid precipitated out, filtered, washed with water, and dried to obtain 22.8 g of a pink solid oxide, namely 6-chloro-2-hydroxyquinoxaline-4-oxide.
[0023] Step (2): Reduction of 6-chloro-2-hydroxyquinoxaline-4-oxide
[0024] Add 22g of the product of step (1) (dissolved in an aqueous alkali metal hydroxide solution), 150ml of N,N-dimethylformamide, and 15g of trimethyl phosphite into the reaction flask, stir and slowly raise the temperature to 110°C, and keep the temperature for 4 hour, filtered while it was hot, discarded the filter residue, precipitated the filtrate, and recrysta...
Embodiment 2
[0028] Step (1) is identical with embodiment 1.
[0029] Step (2): Add 22g of the product obtained in step (1) (dissolved in an aqueous alkali metal hydroxide solution), 110ml of N,N-dimethylformamide, 10.5g of phosphorous acid into the reaction flask, stir and heat up to 110°C , kept the reaction for 9 hours, filtered, discarded the filter residue, precipitated the filtrate, and recrystallized to obtain 15 g of the reduced product, namely 6-chloro-2-hydroxyquinoxaline.
[0030] Step (3): Add 12g of 6-chloro-2-hydroxyquinoxaline, 2.3g of DMF, and 120ml of toluene into the reaction flask, stir, heat up to reflux, then slowly add 21g of thionylchloride dropwise, and the dropwise addition time is about 1 hour . After the dropwise addition, continue to reflux for 4 hours and then stop the reaction. Add 40ml of water to the system, stir properly and let it stand for stratification. The oil layer is washed with water, desolventized, and a solid is precipitated. After filtration, t...
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Abstract
The invention discloses a method for preparing 2-quinoxalinol, which comprises the following steps: preparing 2-quinoxalinol-4-oxide by the cyclization of chloro-m-nitroacetoacetanilide serving as a raw material in the presence of a hydroxide; and preparing 2-quinoxalinol by reducing the 2-quinoxalinol-4-oxide with phosphorous acid or trimethyl phosphate serving as a reducer. In the invention, the phosphorous acid or trimethyl phosphate is used as a reducer to reduce 2-quinoxalinol-4-oxide with high selectivity to prepare 2-quinoxalinol, so the byproducts are reduced, and product yield and purity are high; the conditions of the reduction reaction are mild, and the possibility of explosion generated by low-pressure catalytic hydrogenation with hydrogen serving as a reducer is lowered; because the phosphorous acid or trimethyl phosphate commodity serving as the reducer is cheap and readily available, the production cost of the 2-quinoxalinol is reduced; and as the reaction raw materialsand the products produced in the reaction process are nontoxic, the method contributes to environmental protection.
Description
technical field [0001] The invention belongs to the field of compound preparation. In particular, it relates to a preparation method of 2-quinoxalinol. Background technique [0002] 2-quinoxalinol compounds, such as 2-hydroxy-6-chloroquinoxaline, are well-known intermediates in the production of pharmaceutical chemicals and agrochemicals, generally through the synthesis of 2-quinoxalinol-4-oxide Prepared by selective reduction. [0003] US Patent US4620003 discloses a method for reducing 2-quinoxalinol-4-oxide to 2-quinoxalinol compound. In the method, in the presence of Raney nickel catalyst and alkali metalhydroxide, alkaline earth metalhydroxide or ammonium hydroxide, hydrazine is used as reducing agent to react with 2-quinoxalinol-4-oxide to obtain 2- Quinoxalinol compounds. [0004] US Patent No. 4,636,562 discloses a method for preparing 2-chloro-6-haloquinoxaline compounds from corresponding 4-halo-2-nitroanilines. The method uses hydrogen as a reducing agent, ...
Claims
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