A Facile Synthesis of 3,4-Dialkoxythiophenes through Decarboxylation Catalyzed by Metal Phthalocyanines

3,4-Dialkoxythiophenes are electron rich and their polymers have a narrow energy gap, so they have recently attracted considerable attention in the field of organic semiconducting materials. However, the traditional synthetic approach suffers from some drawbacks, so the development of efficient methods for the synthesis of 3,4-dialkoxythiophenes is needed. A novel, efficient decarboxylation of 2,5-dicarboxy-3,4-dialkoxythiophenes were achieved in excellent yields (up to 95%) and purities using metal phthalocyanines in water, which avoids the use of organic polar solvents, and the recovered catalyst was successfully used in subsequent reactions. Furthermore, the desired products, 3,4-dialkoxythiophenes, were conveniently separated by steam distillation. This method has several advantages such as environmental friendliness, ease of manipulation, and a short reaction time. This environmentally friendly procedure represents a promising green route for the decarboxylation of these important compounds.

摘要采用浸渍法、共沉淀法、水热法和碳微球硬模板法制备了 Ni/ZnO 催化剂, 运用 X 射线衍射、程序升温还原、透射电子显微镜和氢滴定等手段对其进行了表征, 并用于连续固定床反应器中无外加氢气条件下的丙三醇重整-氢解反应. 结果表明, 在较低空速下, 生成的 1,2-丙二醇 (1,2-PDO) 易在 Ni 分散度较高的催化剂上进一步裂解为乙醇和气相产物; 而在较高空速下, 其选择性受制于中间产物丙酮醇的加氢. 在优化的空速下, Ni 分散度越高越有利于 1,2-PDO 的生成. 在 Ni 分散度最高的 Ni/ZnO 催化剂上, 当丙三醇质量空速为 0.84 h–1 时, 1,2-PDO 选择性最高, 为 54.9%, 丙三醇转化率为 85.4%.

A novel, efficient synthesis of 3,4-dialkoxythiophenes by the decarboxylation of 2,5-dicarboxy-3,4-dialkoxythiophenes was achieved in excellent yields using metal phthalocyanines as recyclable catalysts in water under environmentally benign and mild conditions.Figure optionsDownload as PowerPoint slide