Study On The Bromination Reaction Of Thiophene

Thiophene is an important class of organic compounds and has important applications in pesticides,medicines and optoelectronic materials.Bromination of thiophene is an important type of organic reaction.The product bromothiophene is widely used in the design and synthesis of various new drugs and advanced materials.Generally,the alpha position of thiophene is more active than the beta position,and the reaction mainly obtains the brominated product at the alpha position.For polythiophene systems,there are still some challenges for their selective bromination due to their many reaction sites.BDD monomer,chemical name is 1,3-bis(5-bromothiophen-2-yl)-5,7-bis(2-ethylhexyl)benzo [1,2-c:4,5-c’] dithiophene-4,8-dione,is an important intermediate for organic synthesis and has important applications in the synthesis of conjugated polymer donor materials.The development of an efficient synthetic method for BDD monomers can not only reduce the cost of organic solar cell materials,but also provide convenience for the development of new conjugated polymers.This thesis mainly includes the following three aspects:1.A literature review of the research progress on the bromination reaction of thiophene was conducted,and the advantages and disadvantages of various bromination reagents were summarized.Bromination reagents for thiophene include liquid bromine,hydrobromic acid,N-bromosuccinimide(NBS),and other bromination reagents.2.We selected 3-ethylthiophene as a substrate,and systematically examined bromination reagents,solvents,temperatures,catalysts,and substrate equivalent ratios.The optimal conditions are protonic acid as the catalyst,the equivalent ratio of the substrate 3-ethylthiophene and the bromination reagent NBS is 1:2,the dichloromethane is used as the solvent,and the substrate concentration is 0.2 mol / L.The target product was 2,5-dibromo-3-ethylthiophene with 95% of the product.3.The above bromination system was applied to the synthesis of BDD monomer,and satisfactory results were obtained.BDD monomer was synthesized quickly and with high yield(greater than 95%)by using NBS as the bromination reagent and feeding at the equivalent ratio and using dichloromethane as the solvent.