Abstract

A way of hydrodebrominating 2,3,4,5-tetrabromothiophene (1) to 3,4-dibromothiophene (2) on a 5% Pd/Sibunit catalyst is proposed. The effect of solvent, alkaline agent, temperature, and concentration of 1 on the yield of 2 is studied. The optimum conditions are catalyst : substrate mass ratio, 1:10; temperature, 80°С; H₂ pressure, 0.7 MPa; solvent, dimethylformamide; alkaline agent, triethylamine in amounts of 2.2 mol per 1 mol of substrate 1. The yield of 2 is 97.5% in this case. The catalyst can be reused in at least 15 cycles with high yields of 2. The new approach appears to be highly productive with little waste, compared to the conventional chemical reduction of 1 with zinc in CH₃COOH.

中文翻译：

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钯催化剂上氢气选择性催化加氢脱溴 2,3,4,5-四溴噻吩

摘要

提出了一种在 5% Pd/Sibunit 催化剂上将2,3,4,5-四溴噻吩 ( 1 ) 加氢脱溴为 3,4-二溴噻吩 ( 2 )的方法。研究了溶剂、碱剂、温度和1的浓度对2产率的影响。最佳条件为催化剂:底物质量比为1:10; 温度，80°С；H ₂压力，0.7MPa；溶剂，二甲基甲酰胺；碱性剂，三乙胺，用量为每1摩尔底物1 2.2摩尔。在这种情况下2的产率为97.5%。该催化剂可重复使用至少15次，收率高达2 . _{与在 CH 3} COOH中用锌化学还原1的传统方法相比，这种新方法似乎生产率很高，而且几乎没有浪费。