We report the Pd(II)-catalyzed, bidentate directing group 8-aminoquinoline or 2-(methylthio)aniline-assisted β-C-H arylation, alkylation, benzylation and methoxylation of carbazole-3-carboxamide, carbazole-2-carboxamide substrates and construction of C2,C3,C4 functionalized carbazole motifs. The Pd(II)-catalyzed β-C-H arylation reaction was attempted using different directing groups such as 8-aminoquinoline, 2-(methylthio)aniline, 4-amino-2,1,3-benzothiadiazole, 4-methoxyquinolin-8-amine and butan-1-amine. Through optimization of reactions, the 8-aminoquinoline and 2-(methylthio)aniline were found to be suitable directing groups and especially, 2-(methylthio)aniline was found to be an efficient directing group in the Pd(II)-catalyzed β-C-H arylation, alkylation, methoxylation of carbazole-3-carboxamide, carbazole-2-carboxamide substrates. An ample number of β-C-H arylated, alkylated, benzylated and methoxylated carbazole-3-carboxamides were synthesized. The structures of representative β-C(2)-H arylated carbazole and β-C(2)-H methoxylated carbazole motifs were unequivocally confirmed by the single-crystal X-ray structure analysis. Given the wide range of applications of carbazoles in chemical, materials sciences and medicinal chemistry and there have been constant efforts for developing new methods and synthesizing functionalized carbazoles. This work contributes to the expansion of the library of the C2,C3,C4 functionalized carbazole motifs through the Pd(II)-catalyzed directing group-aided site-selective β-C-H activation and functionalization of carbazole-3-carboxamides.
我们报告了
钯(II)催化的双臂定向基团
8-氨基喹啉或 2-(甲
硫基)
苯胺辅助的 β-C-H 芳基化、烷基化、苄基化和甲氧基化
咔唑-3-甲酰胺、
咔唑-2-甲酰胺底物以及 C2、C3、C4 功能化
咔唑基团的构建。尝试使用不同的指导基团,如
8-氨基喹啉、2-(甲
硫基)
苯胺、
4-氨基-2,1,3-苯并噻二唑、
4-甲氧基喹啉-8-胺和丁-1-胺,来催化 β-C-H 芳基化反应。通过优化反应,发现
8-氨基喹啉和 2-(甲
硫基)
苯胺是合适的指导基团,尤其是 2-(甲
硫基)
苯胺在
钯(II)催化的
咔唑-3-甲酰胺和
咔唑-2-甲酰胺底物的β-C-H 芳基化、烷基化、甲氧基化反应中是一个有效的指导基团。合成了大量 β-C-H 芳基化、烷基化、苄基化和甲氧基化的
咔唑-3-甲酰胺。代表性的 β-C(2)-H 芳基化
咔唑和 β-C(2)-H 甲氧基化
咔唑基团的结构已通过单晶 X 射线结构分析得到明确证实。鉴于
咔唑在
化学、材料科学和药物
化学中的广泛应用,人们一直在努力开发新方法和合成功能化
咔唑。这项研究通过 Pd(II)- 催化定向基团辅助的
咔唑-3-羧酰胺的位点选择性 β-C-H 活化和功能化,为扩展 C2、C3、C4 功能化
咔唑基团库做出了贡献。