Cross-coupling of aromatic bromides with allylic silanolate salts.
Cross-coupling of aromatic bromides with allylic silanolate salts.
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DOI：
10.1021/ja805951j
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发表时间：
2008-12-03
影响因子：
15
通讯作者：
Werner, Nathan S.
中科院分区：
文献类型：
--
作者：
Denmark, Scott E.;Werner, Nathan S.
烯丙基二甲基硅烷醇和2-丁烯基二甲基硅烷醇的钠盐与各种芳基溴进行钯催化的交叉偶联，得到烯丙基化和巴豆基化芳烃。两种硅烷醇酯的偶联需要广泛的优化，以高产率提供预期的产物。烯丙基二甲基硅烷醇盐的反应在85 °C下在DME中与烯丙基氯化钯二聚体（2.5摩尔%）发生，以提供7-95%产率的烯丙基化产物。富电子和空间位阻溴化物反应顺利，而贫电子溴化物交叉偶联产率低，因为二次异构化的1-丙烯基异构体（和随后的聚合）。2-丁烯基二甲基硅烷醇盐（E/Z，80：20）需要额外的优化以最大化支链（γ-取代产物）的形成。加入的烯烃（二亚苄基丙酮和降冰片二烯）的显着影响导致了良好的选择性，富电子和贫电子的溴化物在4-83%的产率。然而，含有配位基团（特别是在邻位）的溴化物的选择性较低，在一种情况下甚至相反。与纯的Z-硅醇盐相比，纵向均质的E-硅醇盐的γ-选择性略高。一个统一的机制图片涉及初始γ-金属转移，然后直接还原消除或σ-π异构化可以合理化所有观察到的趋势。
The sodium salts of allyldimethylsilanol and 2-butenyldimethylsilanol undergo palladium-catalyzed cross-coupling with a wide variety of aryl bromides to afford allylated and crotylated arenes. The coupling of both silanolates required extensive optimization to deliver the expected products in high yields. The reaction of the allyldimethylsilanolate takes place at 85 °C in DME with allylpalladium chloride dimer (2.5 mol %) to afford 7–95% yields of the allylation products. Both electron-rich and sterically-hindered bromides reacted smoothly, whereas electron-poor bromides cross-coupled in poor yield because of a secondary isomerization to the 1-propenyl isomer (and subsequent polymerization). The 2-butenyldimethylsilanolate (E/Z, 80:20) required additional optimization to maximize the formation of the branched (γ-substitution product). A remarkable influence of added alkenes (dibenzylideneacetone and norbornadiene) led to good selectivities for electron-rich and electron-poor bromides in 4–83% yields. However, bromides containing coordinating groups (particularly in the ortho position) gave lower, and in one case even reversed, selectivity. Configurationally homogeneous E-silanolates gave slightly higher γ-selectivity than the pure Z-silanolates. A unified mechanistic picture involving initial γ-transmetalation followed by direct reductive elimination or σ–π isomerization can rationalize all of the observed trends.
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影响因子：
15
作者：
Denmark, SE;Sweis, RF
通讯作者：
Sweis, RF
影响因子：
15
作者：
Aranyos, A;Old, DW;Buchwald, SL
通讯作者：
Buchwald, SL
影响因子：
2
作者：
Denmark, Scott E.;Smith, Russell C.
通讯作者：
Smith, Russell C.
影响因子：
5.2
作者：
Denmark, SE;Baird, JD
通讯作者：
Baird, JD
DOI：
10.1039/c39870001236
发表时间：
1987-08-15
影响因子：
--
作者：
BACKVALL, JE;GOGOLL, A
通讯作者：
GOGOLL, A