Mischmetall, an alloy of the light lanthanides, has been used in a variety of organicreactions, either as a coreductant in samarium(II)-mediated reactions (Barbier and Grignard-type reactions, pinacoliccouplingreactions) or as the promoter of Reformatsky-type reactions. It has been also employed as the starting material for easy syntheses of lanthanide trihalides, the reactivity of which has been
作者:Helen C. Aspinall、Nicholas Greeves、Carine Valla
DOI:10.1021/ol050256f
日期:2005.5.1
of samarium diiodide (SmI(2)) with tetraglyme catalyzes the intermolecular pinacolcoupling of aromatic or aliphatic aldehydes at loadings of 10 mol % in the presence of Me(2)SiCl(2) and Mg. Diastereoselectivity of up to 95/5 (+/-/meso) has been achieved for aliphatic aldehydes and up to 19/81 (+/-/meso) for aromatic aldehydes. De values of up to 99% have been achieved in intramolecular pinacol coupling
A new convenient preparation of samarium dibromide in THF is reported. Pinacolcoupling reactions using SmBr2 in catalytic amounts together with mischmetall as a coreductant have been performed with a variety of carbonylcompounds.
The scalable pinacol coupling reaction utilizing the inorganic electride [Ca<sub>2</sub>N]<sup>+</sup>·e<sup>−</sup> as an electron donor
作者:Ye Ji Kim、Sun Min Kim、Hideo Hosono、Jung Woon Yang、Sung Wng Kim
DOI:10.1039/c4cc00802b
日期:——
An inorganic electride [Ca2N]+·e− is used as an efficient electron donor for the scalable pinacol coupling reaction with a high yield.
一种无机电子亚胺[Ca2N]+·e−被用作可扩展的高产率品可醇偶联反应的高效电子给体。
The reduction of α-silyloxy ketones using phenyldimethylsilyllithium
作者:Ian Fleming、Richard S. Roberts、Stephen C. Smith
DOI:10.1039/a709114a
日期:——
diol PhCH(OH)CH(OH)Ph 39. The reaction between phenyldimethylsilyllithium and the acyloin silyl ether 8d (R = But) does not give the ketone ButCH2COBut, but gives instead the anti-Felkin meso diol ButCHOHCHOHBut 40 also with high selectivity (Scheme 12). Silyllithium and some related reagents react with trifluoromethylketones 46 and 48 to give α,α-difluoro silyl enol ethers 47 and 49 (Scheme 14).
苯基二甲基甲硅烷基锂与酰氯甲硅烷基甲醚RCH(OSiMe 3)COR 8反应生成区域定义的甲硅烷基烯醇醚RCH C(OSiMe 2 Ph)R 9,并因此通过水解酮RCH 2 COR 10产生。收率可能很高,但通常是中等水平。建立这种减少的机制涉及布鲁克重排(方案6)而不是彼得森消除(方案1)。尽管在每种情况下机理似乎都是相同的,但甲硅烷基烯醇醚9的立体化学在芳族系列(R = Ph,方案7)和脂族系列(R =环己基,方案8)中在意义上是相反的,主要的芳族甲硅烷基烯醇醚是热力学上较不稳定的异构体E -PhCH C(OSiMe 2Ph)Ph E -9aa和主要的脂族甲硅烷基烯醇醚是热力学更稳定的异构体Z -cC 6 H 11 CH C(OSiMe 2 Ph)-cC 6 H 11 Z -9ba。这是芳族系列中反反费尔金攻击的结果。与甲硅烷基的反应醚卜吨CH(OSiMe 3)COPH图13b是在给予正常Ž