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 mixture of samarium(II) iodide and samarium can induce a coupling reaction of three molecules of alkanoyl halide to give trialkylcarbinols of 2-hydroxy-1,3-diones. When aliphatic, unbranched alkanoyl chlorides are used, this new coupling reaction provides trimeric products as the main reaction products. Tetrahydropyran (THP) proved superior as the solvent because no ring-opening and subsequent reaction
碘化钐 (II) 和钐的混合物可以诱导三分子烷酰卤的偶联反应,生成 2-羟基-1,3-二酮的三烷基甲醇。当使用脂肪族无支链烷酰氯时,这种新的偶联反应提供了三聚产物作为主要反应产物。四氢吡喃 (THP) 作为溶剂被证明是优越的,因为在反应条件下没有观察到开环和随后与烷酰卤的反应,这与使用 THF 时不同。
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
Facile pinacol coupling of aliphatic ketones by Brook rearrangement in the presence of samarium species
作者:Xincan Wang、Guanqun Xie、Yanfei Zhao、Ke Zheng、Yanxiong Fang、Xiaoxia Wang
DOI:10.1016/j.tetlet.2021.153069
日期:2021.5
Herein we report a practical pinacol coupling reaction, in which ketones (aldehydes) react smoothly with Sm and TMSBr to afford the diol products with Sm(II) or (III) siliyl species generated in situ. This reported method affords poor yields for aromatic ketone substrates and good yields for aliphaticketones. Therefore, it distinguishes from most reductive coupling approaches that are more effective for