Snapshot of the Palladium(II)-Catalyzed Oxidative Biaryl Bond Formation by X-ray Analysis of the Intermediate Diaryl Palladium(II) Complex
Snapshot of the Palladium(II)-Catalyzed Oxidative Biaryl Bond Formation by X-ray Analysis of the Intermediate Diaryl Palladium(II) Complex
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DOI：
10.1002/chem.201103576
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发表时间：
2012-01-01
影响因子：
4.3
通讯作者：
Knoelker, Hans-Joachim
中科院分区：
文献类型：
--
作者：
Gensch, Tobias;Roennefahrt, Marika;Knoelker, Hans-Joachim
钯 (II) 催化的通过双芳基 C-H 键活化的氧化 C-C 偶联反应已成为有机合成中的一种有价值的工具。 [1] Kermark等人报道，这种转化的起源之一是钯介导的二芳基胺1a和二芳基醚1b氧化环化为咔唑2a和二苯并呋喃2b。 1975 年（方案 1）。[2]咔唑生物碱因其具有挑战性的结构和有用的生物活性而成为天然产物化学中有吸引力的目标。[3]因此，kermark 等人描述的转换。尽管实际上钯是化学计量的，但已应用于咔唑生物碱的全合成。 [4]受到著名的 Wacker 工艺 [5] 和 Kibayashi 等人的早期工作的鼓励，[6] 我们于 1994 年描述了第一个 palla-ACHTUNGTRENNUNGdium (II) 催化氧化环化为咔唑的例子，通过使用铜 (II) 盐将钯 (0) 再氧化为 pallaACHTUNGTRENNUNGdium (II)。 [7, 8]随后，其他试剂（叔丁基过氧化氢、氧气或空气）也被证明可用于此过程中生成的钯 (0) 的再氧化。 [9]在我们正在进行的针对生物活性咔唑生物碱全合成的计划过程中，[3]我们优化了钯 (II) 催化的氧化环化，并描述了许多应用
Palladium (II)-catalyzed oxidative CÀC coupling reactions by twofold aryl CÀH bond activation have emerged as a valuable tool in organic synthesis.[1] One of the origins of this transformation is the palladium-mediated oxidative cyclization of diarylamines 1a and diaryl ethers 1b to carbazoles 2a and dibenzofurans 2b reported by kermark etal. in 1975 (Scheme 1).[2]Carbazole alkaloids are attractive targets in natural product chemistry because of their challenging structures and useful biological activities.[3] Therefore, the transformation described by kermark et al. has been applied to the total synthesis of carbazole alkaloids despite the fact that it was stoichiometric in palladium.[4] Encouraged by the wellknown Wacker process [5] and earlier work of Kibayashi et al.,[6] we described in 1994 the first example of a palla-ACHTUNGTRENNUNGdium (II)-catalyzed oxidative cyclization to carbazoles by using copper (II) salts for the reoxidation of palladium (0) to pallaACHTUNGTRENNUNGdium (II).[7, 8] Subsequently, other reagents (tert-butyl hydroperoxide, oxygen, or air) have also proven to be useful for the reoxidation of the palladium (0) generated in this process.[9] In the course of our ongoing program directed towards the total synthesis of biologically active carbazole alkaloids,[3] we have optimized the palladium (II)-catalyzed oxidative cyclization and described numerous applications to