Catalytic Transfer Hydrogenation Using Biomass as Hydrogen Source
作者:Srimanta Manna、Andrey P. Antonchick
DOI:10.1002/cssc.201801770
日期:2019.7.5
entities in a fundamentally important process, such as hydrogenation. Various carbohydrates, starch, and lignin were used for stereoselective hydrogenation. Employing a transition metal catalyst and a novel catalytic system, the reduction of alkynes, alkenes, and carbonyl groups with high yields was demonstrated. The regioselective hydrogenation to access different stereoisomers was established by simple
作者:Shun Wang、Nanjundappa Lokesh、Johnny Hioe、Ruth M. Gschwind、Burkhard König
DOI:10.1039/c9sc00711c
日期:——
carbonyl groups in a single reaction are less explored. Here, we report a photoredox-catalysis that uses B2pin2 as terminal reductant and oxygen trap allowing for deoxygenative olefination of aromaticaldehydes under mild conditions. This strategy provides access to a diverse range of symmetrical and unsymmetrical alkenes with moderate to high yield (up to 83%) and functional-group tolerance. To follow
羰基-羰基烯化反应,即 McMurry 反应,代表了构建烯烃的有力策略。然而,在单个反应中直接偶联两个羰基的催化变体的探索较少。在这里,我们报告了一种使用 B 2 pin 2的光氧化还原催化作为末端还原剂和氧阱,允许在温和条件下对芳族醛进行脱氧烯化。该策略提供了获得各种对称和不对称烯烃的途径,具有中等至高产率(高达 83%)和官能团耐受性。为了遵循反应途径,进行了一系列实验,包括自由基抑制、氘标记、荧光猝灭和循环伏安法。此外,结合 NMR 研究和 DFT 计算来检测和分析三种活性中间体:环状三元阴离子物质、α-氧硼基碳负离子和 1,1-苄基二硼酸酯。基于这些结果,我们提出了一种 C C 键生成机制,涉及顺序自由基硼化、“bora-Brook”重排、B 2pin 2介导的脱氧和硼-维蒂希过程。
Energy-Transfer-Mediated Photocatalysis by a Bioinspired Organic Perylenephotosensitizer HiBRCP
triplet energy was greatly improved, and then, it could markedly promote the efficient geometrical isomerization of alkenes from the E-isomer to the Z-isomer. Moreover, it was also effective for energy-transfer-mediated organometallic catalysis, which allowed realization of the cross-coupling of aryl bromides and carboxylic acids through efficient energy transfer from HiBRCP to nickel complexes. Thus, the
Unequivocal Experimental Evidence for a Unified Lithium Salt-Free Wittig Reaction Mechanism for All Phosphonium Ylide Types: Reactions with β-Heteroatom-Substituted Aldehydes Are Consistently Selective for<i>cis</i>-Oxaphosphetane-Derived Products
作者:Peter A. Byrne、Declan G. Gilheany
DOI:10.1021/ja300943z
日期:2012.6.6
erythro-β-hydroxyphosphonium salt) in reactions involving aldehydes bearing heteroatom substituents in the β-position. The effect operates with both benzaldehydes and aliphatic aldehydes and is shown not to operate in the absence of the heteroatom substituent on the aldehyde. The discovery of an effect that is common to reactions of all ylide types strongly argues for the operation of a common mechanism in all Li
protonolysis of the Ir–C(vinyl) bond. Instead, mechanistic data are consistent with an anion-involved alcoholysis pathway involving ionization of (NCP)IrCl(vinyl) via EtOH-for-Cl substitution and reversible protonation of Cl– ion with an Ir(III)-bound EtOH, followed by β-H elimination of the ethoxy ligand and C(vinyl)–H reductive elimination. The use of an amine is key to the monohydride mechanism by promoting