作者:Eduardo Moreno、Luca Antonio Nolasco、Lorenzo Caggiano、Richard F. W. Jackson
DOI:10.1039/b609360d
日期:——
The efficient and direct synthesis of protected biaryl amino acids, including dityrosine (50% overall yield over 3 steps), by Negishi cross-coupling of the serine-derived organozinc reagent 4 with iodo- and di-iodobiaryls, is reported. An improved, although still not perfect, diiodination of 2,2′-biphenol has been achieved using NMe3BnICl2–ZnCl2. Protection of phenolic hydroxyl groups as acetates, rather than benzyl ethers, is required for efficient cross-coupling, and evidence for acetyl migration has been observed during debenzylation of a substituted 2-acetoxy-2′-benzyloxybiaryl. Aromatic C–I to C–Cl conversion has been detected as a minor reaction pathway in the palladium-catalyzed coupling of aryl iodide 3b with organozinc reagent 4.
据报道,通过丝氨酸衍生的有机锌试剂 4 与碘和二碘芳基的 Negishi 交叉偶联,高效直接地合成了受保护的双芳基氨基酸,包括双酪氨酸(3 个步骤的总收率为 50%)。使用 NMe3BnICl2-ZnCl2 实现了 2,2′-联苯酚的改进型二碘化反应,尽管还不够完美。酚羟基作为乙酸酯而不是苄基醚进行保护是高效交叉偶联的必要条件,在取代的 2-乙酰氧基-2′-苄氧基芳基的去苄基化过程中观察到了乙酰基迁移的证据。在钯催化的芳基碘化物 3b 与有机锌试剂 4 的偶联反应中,发现芳香族 C-I 到 C-Cl 的转化是一个次要的反应途径。