5-Bromo-1-pentene was used in stereoselective synthesis of 7α-(3-carboxypropyl) estradiol. It was used in preparation of thioacetate 11 of sialic acid having thioglycosidic linkage. It was also used as staring material in recent syntheses of DL-histrionicotoxin and benzophenone-containing fatty acids.

A new method for synthesizing 5-Bromo-1-pentene

5-Bromo-1-penten (5-bromo-1-penten), molecular formula C5H9Br, molecular weight is 149.03, colorless and transparent liquid. The molecular structure contains both double bonds and bromine atoms, so it has the properties of olefins and halogenated hydrocarbons. It is the starting material for the synthesis of DL-histrionicotoxin and fatty acids containing phenone. It is a basic chemical industry. Pharmaceutical intermediates are widely used in the fields of medicine, pesticides and material chemistry.[1]

At present, the commonly used synthetic methods of 5-bromo-1-pentene mainly include the following: US Patent No. 5,563,230 uses 1,5-dibromopentane as a raw material, heats it with hexamethylphosphoric triamide (HMPA) at high temperature, and removes one molecule of hydrogen bromide to obtain the target compound. However, this process has a large amount of 1,4-pentadiene, which is the by-product of removing two molecules of hydrogen bromide. In addition, the yield reported by the US patent is only 61.5%. The solvent and elimination catalyst used are hexamethylphosphoric triamide, the market price is relatively high, the carcinogenic toxicity is high, and the reaction problem is above 195°C. Due to the high price of raw materials and harsh production conditions, this method is not suitable for production.

Comprehensive analysis of the above various synthesis methods, there is an urgent need for a new 5-bromo-1-pentene process synthesis method that can simplify the existing synthesis process and post-treatment, increase the reaction yield, improve the stability of production and reduce the production cost.

In view of the above problems, the present invention provides a novel 5-bromo-1-pentene process synthesis method that can simplify the existing synthesis process and post-treatment, increase the reaction yield, improve the stability of production and reduce the production cost. In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions: In the present invention, a new chemical synthesis method of 5-bromo-1-pentene, using 1,5-dibromopentane as starting material, N,N-dimethylformamide as solvent, heating; Methylphosphoric triamide is used as a catalyst reaction, and the crude product of 5-bromo-1-pentene is obtained by distillation under normal pressure; the crude product is washed twice with brine, and then rectified to obtain the pure product, which is high-purity 5-bromo-1-pentene The process route is as follows: 1，5-Dibromopentane 100KG, N,N-dimethylformamide 200KG, stir and mix, then heat in an oil bath at 150°C for 6 hours, and collect fractions by atmospheric distillation. The collected fractions are washed twice with 100KG saturated brine, and the upper organic liquid is passed through Distillation to obtain 32.6KG, yield 50.2%, content: 99%.

The product was confirmed to be 5-bromo-1-pentene with a purity of 99% (GC). Among them, the product's 1H NMR (400MHz, CDCl3) δ: 1.96 (m, 2H) 2.22 (m, 2H), 3.43 (t, 2H), 5.02～5.12 (m, 2H), 5.80 (m, 1H).

The advantages and beneficial effects of the present invention are: providing a novel 5-bromo-1-pentene process synthesis method that can simplify the existing synthesis process and post-treatment, increase the reaction yield, increase the stability of production and reduce the production cost. In the present invention, when 1,5-dibromopentane and DMF are mixed and heated, the fraction is distilled out by heating at 100-160°C, the process is simple; the raw materials used are cheap and easy to obtain, and are environmentally friendly; the synthesis method is easy to operate , And the yield is over 80%, and the purity is over 99%; it is suitable for large-scale industrial production. The specific implementation of the present invention will be further described below in conjunction with examples. The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and cannot be used to limit the protection scope of the present invention.

A new chemical synthesis method of 5-bromo-1-pentene, using 1,5-dibromopentane as the starting material, N,N-dimethylformamide as the solvent, heating; using hexamethylphosphorus Triamide is used as a catalyst to react, and the crude product of 5-bromo-1-pentene is obtained by distillation at atmospheric pressure; the crude product is washed twice with brine, and then rectified to obtain the pure product, which is high-purity 5-bromo-1-pentene.

References

[1]PLUS SCIENCE TECH SHANGHAI - CN108046980, 2020, B