Accessing Difluoromethylated and Trifluoromethylated
<i>cis</i>
‐Cycloalkanes and Saturated Heterocycles: Preferential Hydrogen Addition to the Substitution Sites for Dearomatization
作者:Xue Zhang、Liang Ling、Meiming Luo、Xiaoming Zeng
DOI:10.1002/anie.201907457
日期:2019.11.18
Reported here is a straightforward process in which a cyclic (alkyl)(amino)carbene/Rh catalyst system facilitates the preferential addition of hydrogen to the substitutionsites of difluoromethylated and trifluoromethylated arenes and heteroarenes, leading to dearomative reduction. This strategy enables the diastereoselective synthesis of cis-difluoromethylated and cis-trifluoromethylated cycloalkanes
Synthesis of 3-Substituted Furans by Hydroformylation
作者:Perli Nanayakkara、Howard Alper
DOI:10.1002/adsc.200505238
日期:2006.3
for the synthesis of 3-substitutedfurans by the hydroformylation of substituted propargylic alcohols is described using rhodium acetate and triphenylphosphine in dichloromethane. The hydroformylation reaction proceeds in a regioselective manner under mild reaction conditions. This novel methodology is versatile and can be applied to the synthesis of a variety of 3-aryl-substituted furans.
A General Palladium-Catalyzed Hiyama Cross-Coupling Reaction of Aryl and Heteroaryl Chlorides
作者:On Ying Yuen、Chau Ming So、Ho Wing Man、Fuk Yee Kwong
DOI:10.1002/chem.201600420
日期:2016.5.4
A general palladium‐catalyzed Hiyama cross‐coupling reaction of aryl and heteroaryl chlorides with aryl and heteroaryl trialkoxysilanes by a Pd(OAc)2/L2 catalytic system is presented. A newly developed water addition protocol can dramatically improve the product yields. The conjugation of the Pd/L2 system and the water addition protocol can efficiently catalyze a broad range of electron‐rich, ‐neutral
Lewis acid enhancement by hydrogen-bond donors for asymmetric catalysis
作者:Steven M. Banik、Anna Levina、Alan M. Hyde、Eric N. Jacobsen
DOI:10.1126/science.aao5894
日期:2017.11.10
used this motif to activate a Lewis acid cocatalyst, pulling a leaving group off silicon instead of carbon (see the Perspective by Mattson). The combined pair of catalysts is more effective for reactions such as asymmetric cycloadditions that involve weaker leaving groups on carbon. Science, this issue p. 761; see also p. 720 A chiral amide activates a silicon-based Lewis acid for joint asymmetric catalysis
路易斯酸催化由标记团队攻克具有两个紧密间隔的氮氢基团的分子催化剂可以像镊子一样发挥作用,通过双氢键锁定离去基团,然后将其拉开,从而激活碳中心。在所得离子对中,催化剂的形状可以使随后的反应偏向于仅有利于两种可能的镜像产物中的一种。巴尼克等人。使用这个主题来激活路易斯酸助催化剂,从硅而不是碳上拉出离去基团(参见 Mattson 的观点)。组合的催化剂对对于涉及碳上较弱离去基团的不对称环加成等反应更有效。科学,本期第 14 页。第761章另见 p. 720 手性酰胺可激活硅基路易斯酸以进行联合不对称催化。小分子双氢键(H键)供体,如脲、硫脲、方酰胺和胍离子,作为促进各种对映选择性反应的有效催化剂而得到广泛应用。然而,这些催化剂仅呈弱酸性,因此需要高反应性的亲电子底物才能有效。我们在这里介绍了一种手性氢键供体的催化活性模式,该模式能够使相对不活泼的亲电子试剂发生对映选择性反应。方酰胺与三氟甲磺酸硅
Sodium Chloride Catalyzed Regioselective Trifluoromethylthiolation of Furans
作者:Frank Glorius、Johannes Ernst、Lena Rakers
DOI:10.1055/s-0036-1588609
日期:——
Here, we report the catalytic trifluoromethylthiolation of furans employing sodium chloride as an inexpensive, abundant and ecologically friendly catalyst. The developed method exhibits perfect regioselectivity and a high functional group tolerance. Furthermore, the robustness of the newly developed method was determined by the additive-based Robustness Screen.