ChemicalBook CAS DataBase List 2,5-Dimethylthiophene-3-boronic acid

2,5-Dimethylthiophene-3-boronic acid synthesis

9synthesis methods

Product Name:2,5-Dimethylthiophene-3-boronic acid
CAS Number:162607-23-0
Molecular formula:C6H9BO2S
Molecular Weight:156.01

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Yield:162607-23-0 73%

Reaction Conditions:

Stage #1:3-bromo-2,5-dimethylthiophene with n-butyllithium in tetrahydrofuran;hexane at -78; for 0.25 h;
Stage #2:boric acid tributyl ester in tetrahydrofuran;hexane at 20; for 8 h;
Stage #3: with hydrogenchloride in tetrahydrofuran;hexane;water for 10 h;

Steps:

2.2.2 Synthesis of (2,5-dimethylthiophen-3-yl)boronic acid (4 [23])
3-Bromo-2,5-dimethylthiophene (2 g, 1 equiv., 10.47 mmol)was dissolved in 40 mL anhydrous tetrahydrofuran (THF). n-Butyllithium (2.5 M in hexane, 6.28 mL, 1.1 equiv.,11.51 mmol) was slowly added at -78 °C, and the reactionsolution was stirred at the same temperature for 15 min. Asolution of tri-n-butyl borate (3.09 mL, 1.1 equiv.,11.51 mmol) in THF (10 mL) was added over a period of10 min. The reaction solution was slowly heated to roomtemperature and stirred for 8 h. Then 9 mL 2 M HCl wasadded and the mixture was stirred for another 10 h. After thereaction was completed, the excess solvent was removed andNaOH solution was added to neutralize. The resulting mixturewas extracted with dichloromethane and water for threetimes before the combined organic phases were dried overMgSO4 and the solvent was removed to obtain a crudeproduct. The crude product was dissolved in 15 mL of dichloromethaneand washed three times with 2 M NaOH solution. The resulting aqueous phases were combined and10 mL concentrated hydrochloric acid (12 M) was addeddropwise to commence the precipitation of 4 in a 73% yield as a white powder (1.2 g). 1H NMR (400 MHz, CDCl3): δ7.07 (s, 1H), 2.82 (s, 3H), 2.46 (s, 3H).

References:

Gu, Luyan;Zhang, Lujia;Luo, Xiao;Zheng, Ying;Ye, Zhiwei;Lv, Meng;Chen, Jinquan;Chen, Chunlai;Xiao, Yi;Zhu, Weihong;Qian, Xuhong;Yang, Youjun [Science China Chemistry,2021,vol. 64,# 2,p. 253 - 262]

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162607-23-0
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References