Method for synthesizing 5-N-tert-butyloxycarbonyl-5-N-methylamino-2-thiophenic acid
A kind of tert-butoxycarbonyl and methylamino technology, applied in the field of raltitrexed intermediate preparation and compound preparation, can solve problems such as being unfavorable to industrialized production, harsh conditions, difficult to operate, etc., and achieve easy industrialized production and easily controllable conditions. , the effect of easy operation
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Embodiment 1
[0054] 1.1 The preparation of compound III i.e. 5-bromothiophene-2-amine
[0055] Dissolve the raw material 2-bromo-5-nitrothiophene (10g48.3mmol) in a mixed solvent of 80ml ethanol and 25ml water, add 10.1g ammonium chloride, add 12.5g iron powder, and slowly heat to 70°C under nitrogen protection , and reacted for 8 hours. After the reaction, when the system was cooled to 50°C, it was filtered while it was hot, and the filtrate was evaporated with a water pump and a rotary evaporator (0.01MPa, 40°C) to remove the organic solvent, and then oiled with an oil pump (0.001MPa). The bath was distilled under reduced pressure, the temperature of the oil bath was 100-120°C, and the fraction was extracted at 80-81°C to obtain 6.9g of compound III with a yield of 80.7%.
[0056] 1 H NMR (CDCl 3 ,400MHz): δ=6.98(s,2H),6.44(d,1H),5.74(d,1H).
[0057] MS (EI): m / e=177.
[0058] 1.2 Preparation of compound III, namely 5-bromothiophene-2-amine
[0059] Dissolve the raw material 2-bromo...
Embodiment 2
[0071] 2.1 Preparation of compound IV i.e. tert-butyl 5-bromothiophene-2-carbamate
[0072] Dissolve the compound III 5-bromothiophene-2-amine (5g, 28.3mmol) obtained in Example 1 in 40ml of methanol, add 3.54g of triethylamine and 7.6g of di-tert-butyl dicarbonate, and react for 4 hours at 25°C ; After the reaction, add 50ml ethyl acetate and 90ml water for extraction, the extraction temperature is 15-20°C, separate the organic phase, first wash the residual alkali in the system with 1M dilute hydrochloric acid, then wash the excess acid with saturated sodium bicarbonate, and finally saturate Wash with sodium chloride solution, dry the organic phase with sodium sulfate, filter with suction, evaporate the filtrate with a water pump and a rotary evaporator (0.01MPa, 40°C) to remove the organic solvent, and obtain 9 g of crude compound IV. Then it was dissolved in a mixed solvent of 36ml ethyl acetate and 12ml petroleum ether, heated to reflux, and after 40min, when it was slowl...
Embodiment 3
[0088] 3.1 Preparation of Compound V, tert-butyl 5-bromothiophene-2-(N-methylamino)carboxylate
[0089] Compound IV 5-bromothiophene-2-carbamate tert-butyl ester (4g, 14.4mmol) obtained in Example 2 was dissolved in 30ml of tetrahydrofuran, and sodium hydride (60wt%) 0.88 g, after reacting for half an hour, add 3.08g of methyl iodide, continue to react at -5-0°C for 0.5 hours, remove the ice bath, and react at room temperature 20°C for 3 hours; under ice bath (-5-0°C), add saturated chlorine ammonium chloride solution, adjust PH=5~6, add 60mL water and 40ml ethyl acetate for extraction, separate the organic phase, wash with saturated sodium chloride solution, dry the organic phase with sodium sulfate, filter with suction, and use a water pump and rotary evaporator for the filtrate (0.01MPa, 40°C) to distill off the solvent to obtain 5.0g of the crude product of compound V, then add a total of 30mL of ethyl acetate and petroleum ether with a volume ratio of 4:1 to dissolve, hea...
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