Synthesis of arylzinc compounds in ethereal solvent and application to organic synthesis

芳基锌化合物ArZnX作为一种反应性和化学选择性的供ar试剂，在有机合成中得到了广泛的应用。与传统的ArLi、ArMgX和ZnX_2合成方法相比，用锌粉在HMPA、DMF或TMU等极性溶剂中处理ArX的方法更方便、原子经济。这里需要注意的是，由于有机锌化合物易受潮，所以含有ArZnX的溶液在随后的反应中使用。因此，给定的溶剂不仅要适合于制备，而且要适合于ArZnX的利用。在这种情况下，极性溶剂可能会限制ArZnX的使用，因为或金属反应通常在极性较低的溶剂中进行，如THF。在本研究中，我们尝试在乙醚溶剂中通过直接反应合成ArZnX。从官能团耐受性和原子经济性（新锌效应）的角度来看，这些化合物必须为有机合成提供极有价值的Ar^-来源。结果表明，含CO_2CH_3、CN、Br、CF_3等吸电子基团的ArI在70℃条件下与Zn粉进行正交反应，得到了理想的ArZnI，收率较高。对于含有CH_3、OCH_3、H等类似的间位或对位吸电子基团或供电子基团的An反应，分别需要在100℃或130℃的二赖氨酸加热。Pd(dba)_2对ArZnX醚溶液与烯丙基卤化物的交叉偶联反应具有优异的催化作用，可高产得多种功能化烯丙苯；反应主要在5 mol%的催化剂存在下，在0℃下进行5 ~ 30 min。此外，TiCl_2(O-i-Pr)_2还介导了乙醚溶剂中醛类与ArZnX的反应。由于钛化合物无法在TMU中介导反应，因此使用醚溶剂是保证反应成功的关键。少

As a reactive and chemoselective Ar-supplying reagent, arylzinc compounds, ArZnX, are extensively utilized in organic synthesis. Compared with the conventional synthetic method of the compounds from ArLi or ArMgX and ZnX_2,the recently developed one of treating ArX with Zn powder in polar solvents such as HMPA, DMF, or TMU is far more convenient and atom economic. Here it is to be noted that, because of the liability of the organozinc compounds to moisture, the solution containing ArZnX is used in subsequent reaction as obtained. Consequently, a given solvent must be appropriate not only for the preparation but also for the utilization of ArZnX. In this context, the polar solvents might limit the utility of ArZnX, since or ganometallic reactions are often carried out in less polar solvent such as THF. In this research, we attempted to synthesize the ArZnX through the direct reaction in ethereal solvents. Such compounds, if available, must provide the extremely valuable sources of Ar^- … More for organic synthesis from viewpoints of functional group tolerance and atom economy (new zinc effect). We found that the reactions of ArI containing electron-withdrawing groups such as CO_2CH_3,CN, Br, or CF_3 at the ortho-position with Zn powder in THE at 70℃ proceed well to afford the desired ArZnI in good yields. For the reactions of An containing similar electron-withdrawing groups at the meta- or para-position or electron-donating groups like CH_3,OCH_3,or H, the heating at 100 or 130 in diglyme was required, respectively. Pd(dba)_2 exhibited an outstanding efficient catalytic effect for the cross-coupling of these ethereal solution of ArZnX with allylic halides to afford a variety of functionalized allylbenzenes in high yields ; the reactions were mostly carried out at 0℃ for 5-30 min in the presence of 5 mol% of catalyst. In addition, TiCl_2(O-i-Pr)_2 mediated the reactions between aldehydes and ArZnX in ethereal solvents, too. Since the titanium compound failed in mediating the reactions in TMU, the utility of ethereal solvents is essential for the successful reaction. Less