5-Pyrimidylboronic acid and 2-methoxy-5-pyrimidylboronic acid: new heteroarylpyrimidine derivatives via Suzuki cross-coupling reactions
作者:Nezire Saygili、Andrei S. Batsanov、Martin R. Bryce
DOI:10.1039/b314624n
日期:——
5-Pyrimidylboronic acid 2 and 2-methoxy-5-pyrimidylboronic acid 4 have been synthesised by lithium-halogen exchange reactions on 5-bromopyrimidine and 2-methoxy-5-bromopyrimidine, respectively, followed by reaction with triisopropylborate. Suzuki cross-coupling reactions of 2 and 4 with heteroaryl halides [Na2CO3, Pd(PPh3)2Cl2, 1,4-dioxane, 95 °C] yield heteroarylpyrimidines (heteroaryl = thienyl, quinolyl and pyrimidyl). Two-fold reaction of 2 with 4,6-dichloropyrimidine 12 gave 4,6-bis(5-pyrimidyl)pyrimidine 8
(56% yield). Reaction of 4,6-dichloropyrimidine with 2-methoxy-5-pyridylboronic acid gave 4,6-bis(2-methoxy-5-pyridyl)pyrimidine 14
(84% yield). Conversion of 14 into 4,6-bis(2-chloro-5-pyridyl)pyrimidine 15
(63% yield) followed by two-fold Suzuki reaction with 4-tert-butylbenzeneboronic acid gave the penta-arylene derivative 4,6-bis[2-(4-tert-butyl)phenyl-5-pyridyl]pyrimidine 16
(16% yield). Analogous reaction of 12 with 2-methoxy-3-pyridylboronic acid 17 gave 4,6-bis(2-methoxy-3-pyridyl)pyrimidine 18
(64% yield). The X-ray crystal structures of compound 2·0.5H2O and compound 18 are reported. The two hydroxyl H atoms in 2 have the usual exo–endo orientation. However, unlike most arylboronic acids, molecule 2 does not form a centrosymmetric hydrogen-bonded dimer. In molecule 18, the pyridine rings form dihedral angles of 39.9° and 22.8° with the central pyrimidine ring.
通过锂-卤交换反应分别在5-溴嘧啶和2-甲氧基-5-溴嘧啶上合成5-嘧啶基硼酸2和2-甲氧基-5-嘧啶基硼酸4,随后与三异丙基硼酸酯反应。2和4与杂环卤化物进行铃木交叉偶联反应(Na2CO3,Pd(PPh3)2Cl2,1,4-二恶烷,95°C)产生杂环嘧啶(杂环=噻吩基、喹啉基和嘧啶基)。2与4,6-二氯嘧啶12的双重反应得到4,6-双(5-嘧啶基)嘧啶8(产率56%)。4,6-二氯嘧啶与2-甲氧基-5-吡啶基硼酸的反应得到4,6-双(2-甲氧基-5-吡啶基)嘧啶14(产率84%)。将14转化为4,6-双(2-氯-5-吡啶基)嘧啶15(产率63%),然后与4-叔丁基苯硼酸进行双重Suzuki反应,得到五芳基衍生物4,6-双[2-(4-叔丁基)苯基-5-吡啶基]嘧啶16(产率16%)。类似地,12与2-甲氧基-3-吡啶基硼酸17反应得到4,6-双(2-甲氧基-3-吡啶基)嘧啶18(产率64%)。报告了化合物2·0.5H2O和化合物18的X射线晶体结构。2中的两个羟基H原子具有通常的外-内取向。然而,与大多数芳基硼酸不同,分子2没有形成中心对称氢键二聚体。在分子18中,吡啶环与中心嘧啶环形成39.9°和22.8°的二面角。