Various functionalized 2-aminobenzo[b]thiophenes have been synthesized at room temperature by the Ullmann coupling reaction for the first time. The enantiospecific coupling reaction has been further demonstrated without loss of optical purity. The newly synthesized 2-anilino-3-cyano-benzo[b]thiophenes are transformed into 11-amino-benzothieno[2,3-b]quinolines in the presence of triflic acid.
各种官能化的2-氨基苯并[ b ]噻吩在室温下首次通过乌尔曼偶合反应合成。已经进一步证明了对映特异性偶联反应,而没有光学纯度的损失。在三氟甲磺酸存在下,将新合成的2-苯胺基-3-氰基-苯并[ b ]噻吩转化为11-氨基-苯并噻吩并[2,3- b ]喹啉。
Copper Catalyzed Intramolecular N-Arylation of Ketene Aminals at Room Temperature: Synthesis of 2-Amino-3-cyanoindoles
Various 2-amino-3-cyanoindoles are synthesized through copper catalyzed intramolecular N-arylations of ketene aminals at room temperature for the first time with 60–99% yields within 0.1–2 h. Controlled regioselective N-arylations of unsymmetrical ketene aminals are also studied. Further, a new double heteroannulation approach is demonstrated for the synthesis of 11-aminoindolo[2,3-b]quinolines from
在室温下首次通过铜催化乙烯酮缩醛的分子内N-芳基化反应合成了各种2-氨基-3-氰基吲哚,其收率在0.1-2 h内达到60-99%。还研究了不对称乙烯酮缩醛的可控区域选择性N-芳基化。此外,从非环和非杂环的前体合成11-氨基吲哚并[2,3- b ]喹啉的新的双异环的方法被证明。
A novel base-promoted intramolecular cyclization approach for the synthesis of benzofurans, benzothiophenes and indoles
作者:Qianqian Zhang、Hanyu Nie、Kun Zhang、He Huang、Chuanjun Song
DOI:10.1016/j.tet.2022.132815
日期:2022.6
A facile transition-metal-free method for the synthesis of benzofuran was developed via potassium t-butoxide promoted intramolecular cyclization of o-bromobenzylketones. This method showed a wide range of substrate tolerability affording substituted benzofurans in moderate to good isolated yields. In addition, thio-ketones and imines could also be converted to corresponding benzothiophenes and indoles
A more sustainable protocol leading to 2-alkyl- or 2-aryl-substituted benzo[b]furans is reported, involving a copper-TMEDA complex which catalyzes the transformation of readily available ketone derivatives into the corresponding benzofurans in good to excellent yields. The reaction is accomplished using water as the solvent without organic cosolvents, and one example of catalyst reutilization is also presented.
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