Facile Photochemical Synthesis of 5,10-Disubstituted [5]Helicenes by Removing Molecular Orbital Degeneracy
摘要:
Photocyclodehydrogenation is a key reaction to synthesize helicenes; however, because of overannulation, it is not applicable to the synthesis of [S]helicene. Introduction of a cyano group was found to remove the orbital degeneracy of the low-lying unoccupied MOs; consequently, the lowest excitation comprises a single transition involving the C-2-antisymmetric MO. Therefore, the problematic overannulation can be effectively suppressed. Moreover, in combination with the Knoevenagel reaction, a one-pot synthesis of 5,10-dicyano[5]helicene with 67% yield was accomplished.
Facile Regio- and Stereoselective Hydrometalation of Alkynes with a Combination of Carboxylic Acids and Group 10 Transition Metal Complexes: Selective Hydrogenation of Alkynes with Formic Acid
作者:Ruwei Shen、Tieqiao Chen、Yalei Zhao、Renhua Qiu、Yongbo Zhou、Shuangfeng Yin、Xiangbo Wang、Midori Goto、Li-Biao Han
DOI:10.1021/ja2069246
日期:2011.10.26
highly stereo- and regioselective hydrometalation of alkynes generating alkenylmetal complex is disclosed for the first time from a reaction of alkyne, carboxylic acid, and a zerovalent group10 transition metal complex M(PEt(3))(4) (M = Ni, Pd, Pt). A mechanistic study showed that the hydrometalation does not proceed via the reaction of alkyne with a hydridometal generated by the protonation of a
Copper-catalysed, diboron-mediated <i>cis</i>-dideuterated semihydrogenation of alkynes with heavy water
作者:Xiaowei Han、Jiefeng Hu、Cheng Chen、Yu Yuan、Zhuangzhi Shi
DOI:10.1039/c9cc03213d
日期:——
efficiently mediate the transfer of two D atoms from heavy water directly onto alkynes through copper-catalysed cis-selective semihydrogenation. Avoiding the use of costly and flammable D2 gas, this safe and practical process can proceed with excellent chemoselectivity and stereoselectivity. Utilizing the present method as the key step, the formal asymmetrictotalsynthesis of d2-deuterium-labeled cis-combretastatin
Ligand-free (<i>Z</i>)-selective transfer semihydrogenation of alkynes catalyzed by <i>in situ</i> generated oxidizable copper nanoparticles
作者:Rafał Kusy、Karol Grela
DOI:10.1039/d1gc01206a
日期:——
of a semihydrogenation reaction results in the formation of a water-soluble ammonia complex, so that the catalyst may be reused several times by simple phase-separation with no need for any special regeneration processes. Formed NH4B(OR)4 can be easily transformed back into ammonia-borane or into boric acid. In addition, a one-pot tandem sequence involving a Suzuki reaction followed by semihydrogenation
在此,我们提出了在氢供体(如氨硼烷和绿色质子溶剂)存在下,基于原位生成的 CuNPs的炔烃的( Z ) 选择性转移半氢化。这种环保方法的特点是操作简单,同时具有高立体选择性和化学选择性以及官能团兼容性。CuNPs在半氢化反应完成后自动氧化形成水溶性氨络合物,因此催化剂可以通过简单的相分离多次重复使用,无需任何特殊的再生过程。形成NH 4 B(OR) 4可以很容易地转化回氨硼烷或硼酸。此外,还提出了涉及 Suzuki 反应和半氢化的一锅串联序列,这可以最大限度地减少化学废物的产生。
Methanol as the Hydrogen Source in the Selective Transfer Hydrogenation of Alkynes Enabled by a Manganese Pincer Complex
作者:Jan Sklyaruk、Viktoriia Zubar、Jannik C. Borghs、Magnus Rueping
DOI:10.1021/acs.orglett.0c02151
日期:2020.8.7
The first base metal-catalyzed transfer hydrogenation of alkynes with methanol is described. An air and moisture stablemanganesepincer complex catalyzes the reduction of a variety of different alkynes to the corresponding (Z)-olefins in high yields. The reaction is stereo- and chemoselective and scalable.
Highly Chemo- and Stereoselective Transfer Semihydrogenation of Alkynes Catalyzed by a Stable, Well-Defined Manganese(II) Complex
作者:Aleksandra Brzozowska、Luis Miguel Azofra、Viktoriia Zubar、Iuliana Atodiresei、Luigi Cavallo、Magnus Rueping、Osama El-Sepelgy
DOI:10.1021/acscatal.8b00983
日期:2018.5.4
unprecedented manganese-catalyzed semihydrogenation of internal alkynes to (Z)-alkenes using ammonia borane as a hydrogen donor. The reaction is catalyzed by a pincer complex of the earth-abundant manganese(II) salt in the absence of any additives, base, or superhydride. The ammonia borane smoothly reduces the manganese precatalyst [Mn(II)–PNP][Cl]2 to the catalytically activespecies [Mn(I)–PNP]–hydride in the