The Suzuki–Miyaura Cross‐Coupling as the Key Step in the Synthesis of 2‐Aminobiphenyls and 2,2'‐Diaminobiphenyls: Application in the Synthesis of Schiff Base Complexes of Zn

• Published in: European journal of organic chemistry 2020-07, Vol.2020 (27), p.4208-4226
• Main Authors: Hylland, Knut Tormodssønn, Øien‐Ødegaard, Sigurd, Tilset, Mats
• Format: Article
• Language: English
• Subjects: Amines; Coordination compounds; Cross coupling; Imines; Ligands; N/O Ligands; Schiff bases; Synthesis; Terphenyls; Zinc
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.202000599

2‐Nitrophenylboronic acids serve as interesting starting materials for the construction of biphenyl‐ and terphenyl‐based amines if subjected to the Suzuki–Miyaura reaction. Unfortunately, these boronic acids suffer from low reactivity in Suzuki reactions, alongside their low stability in the presence of Pd. Herein, a general method for the construction of 2‐nitro‐substituted bi‐ and terphenyls is presented, with special emphasis on the synthesis of 2‐amino‐2'‐nitrobi‐ and terphenyls. Comparisons are made with other boronic acids that have some of the aforementioned issues. Finally, the application of the obtained 2‐amino‐2'‐nitrobi‐ and terphenyls as starting materials for the synthesis of bi‐ and terphenyl based di‐ and triamines is encountered for, with emphasis on the use of these amines as precursors for Schiff base ligands. In addition, the synthesis of some Zn complexes of these ligands is presented. The Suzuki–Miyaura reaction is used as a key step for the synthesis of 2‐aminobiphenyls and 2,2'‐diaminobiphenyls, which in turn can be utilized to make Schiff base complexes of Zn. Special emphasis is on the cross‐coupling reaction between 2‐bromoanilines and a 2‐nitro‐substituted arylboronic acid, for which there is little existing precedence.