Room-temperature alkyl-alkyl Suzuki cross-coupling of alkyl bromides that possess β hydrogens
Room-temperature alkyl-alkyl Suzuki cross-coupling of alkyl bromides that possess β hydrogens
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DOI：
10.1021/ja011306o
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发表时间：
2001-10-17
影响因子：
15
通讯作者：
Fu, GC
中科院分区：
文献类型：
--
作者：
Netherton, MR;Dai, CY;Fu, GC
钯催化有机金属试剂与芳基和乙烯基亲电试剂（eq 1）的偶联已成为生成碳-碳键的经典方法。1不仅可以使用sp2杂化，也可以使用sp3杂化的有机金属。另一方面，钯催化的卤化物/三酸盐sp3杂化的偶联是相当罕见的。烷基卤化物/三氟酸盐对钯的缓慢氧化加成和容易的β-氢化物消除（eq 2）是这种相对缺乏成功的两个可能原因。事实上，到目前为止，大多数钯催化的烷基亲电试剂偶联都涉及被氧化加成激活的底物和缺乏β氢（例如，苄基卤化物）。特别是对于铃木反应，在烷基卤化物/三氟化物中，只有碘化物被证明与任何一般性偶联(Pd (PPh3) 4,60℃；45 - 71%的收益率)。另一方面，据我们所知，还没有发现含有β氢的烷基溴铃木反应的例子。在本通讯中，我们描述了在令人惊讶的温和条件下（室温；eq 3）实现各种烷基溴的铃木交叉偶联的方法。
Palladium-catalyzed couplings of organometallic reagents with aryl and vinyl electrophiles (eq 1) have become classic methods for generating carbon-carbon bonds. 1 Not only sp2-hybridized but also sp3-hybridized organometallics can be employed. On the other hand, palladium-catalyzed couplings in which the halide/triflate is sp3-hybridized are rather uncommon. 1-3Slow oxidative addition of alkyl halides/triflates to palladium and facile β-hydride elimination (eq 2) are two likely causes for this comparative lack of success. Indeed, to date most palladiumcatalyzed couplings of alkyl electrophiles have involved substrates that are activated toward oxidative addition and that lack β hydrogens (eg, benzyl halides). For the Suzuki reaction in particular, among alkyl halides/triflates, only iodides have been shown to couple with any generality (Pd (PPh3) 4, 60 C; 45-71% yield). 4, 5 On the other hand, to the best of our knowledge, there are no examples of Suzuki reactions of alkyl bromides that possess β hydrogens. In this communication, we describe a method for achieving Suzuki cross-couplings of a variety of alkyl bromides under surprisingly mild conditions (room temperature; eq 3).