Copper-Mediated Direct Cross-Coupling of 1,3,4-Oxadiazoles and Oxazoles with Terminal Alkynes
Copper-Mediated Direct Cross-Coupling of 1,3,4-Oxadiazoles and Oxazoles with Terminal Alkynes
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DOI：
10.1002/chem.200902916
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发表时间：
2010-01-01
影响因子：
4.3
通讯作者：
Miura, Masahiro
中科院分区：
文献类型：
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作者：
Kitahara, Masanori;Hirano, Koji;Miura, Masahiro
过渡金属介导的C_2H_4键的直接官能化反应在现代有机化学中引起了极大的兴趣。[1]其中，利用两个不同的C2 H4键的直接氧化交叉偶联反应虽然难以以一般方式实现，但却是相当有吸引力的方法，因为可以消除预活化，例如两种偶联组分的金属化和卤化，使得它们在经济和环境上是有利的（方案1）。因此，许多研究人员最近探索了这种类型的转化，并且sp2/sp2，[2] sp3/sp2，[3] sp3/sp3，[4]和sp/sp C3 H键[5]之间的许多C3 H C键形成反应已经变得可用，特别是在钯催化下。[6]然而，与sp2和sp CNOH键的直接交叉偶联，可以被正式视为Sonogashira型反应的直接版本，仍然是一个重要的挑战。[7]近年来，在直接氧化偶联反应中，廉价易操作的铜盐或铜配合物引起了人们的广泛关注。[8-11] Li描述了铜/过氧化物催化剂体系在活化与烯烃、杂原子和羰基相邻的sp3 C2 OH键中的用途。[8]Kündig [9a]和Cacchi [9 b]分别成功地通过铜盐介导的分子内直接sp3/sp2 C13 C偶联合成了羟吲哚和吲哚。本课题组还报道了铜催化的N，N-二甲基苯胺与末端炔在分子氧作用下的氧化偶联反应。[10]这些有希望的例子鼓励我们开发一种基于铜的方法，该方法直接用于杂芳烃sp2和炔sp C3 H键之间的偶联，作为我们对杂环化合物的直接官能化的研究的一部分。[1b我们已经发现有用的杂芳烃核，例如1，3，4-恶二唑和恶唑，有效地与末端炔进行铜介导的氧化偶联，这在本文中报道。作为某些1，3，4-恶二-
The transition-metal-mediated direct functionalization reactions of CÀH bonds have attracted significant interest in modern organic chemistry.[1] Among them, the direct oxidative cross-coupling reactions utilizing two different CÀH bonds, though difficult to achieve in a general way, are quite attractive processes, since the preactivation, such as metalation and halogenation of both coupling components, can be eliminated so that they are economically and environmentally advantageous (Scheme 1). Therefore, many researchers have recently explored this type of transformation, and a number of CÀC bond formation reactions between sp2/sp2,[2] sp3/sp2,[3] sp3/sp3,[4] and sp/sp CÀH bonds [5] have become available, in particular under palladium catalysis.[6] However, the direct cross-coupling with sp2 and sp CÀH bonds, which may be regarded formally as the direct version of Sonogashira type reaction, still remains an important challenge.[7] Recently, much attention has been focused on tractable and less expensive copper salts or complexes in oxidative direct CÀC coupling reactions.[8–11] Li described the utility of a copper/peroxide catalyst system in the activation of sp3 CÀ H bonds adjacent to olefins, heteroatoms, and carbonyls.[8]Kündig [9a] and Cacchi [9b] succeeded in the synthesis of oxindoles and indoles, respectively, through an intramolecular direct sp3/sp2 CÀC coupling mediated by copper salts. Our group also reported the copper-catalyzed oxidative coupling of N, N-dimethylanilines with terminal alkynes under molecular oxygen.[10] These promising examples encouraged us to develop a copper-based process directed toward the coupling between heteroarene sp2 and alkyne sp CÀH bonds as part of our study on the direct functionalization of heterocyclic compounds.[1b, d, e] We have found that useful heteroarene cores, for example, 1, 3, 4-oxadiazole and oxazole, efficiently undergo copper-mediated oxidative coupling with terminal alkynes, which is reported herein. As certain 1, 3, 4-oxadia-