我们在此详细介绍了骨架镍阴极上水溶液中电催化加氢 (ECH) 的机理研究,以探索与能源科学相关的官能化芳基醚之间还原催化 CO 键裂解的各种途径。芳基醚的多相催化氢解在化石燃料的加氢脱氧和生物质木质素的升级中都很重要。已知简单官能团(如羰基、羟基、甲基或甲氧基)的存在或不存在会导致 sp3 CO 和 sp2 CO 键之间的反应性和裂解选择性发生显着变化。具体而言,已报道的 Ni 和其他催化剂的氢解研究暗示了木质素的 α-酮和 α-羟基 β-O-4 型芳基醚键中 CO 醚键的不同裂解机制。我们的新费率,ECH 反应的选择性和同位素标记结果证实这些芳基醚通过不同的路径进行 CO 裂解。对于简单的 2-苯氧基-1-苯基乙烷或其醇同系物 2-苯氧基-1-苯基乙醇,苄基位点通过 Ni CH 插入激活,然后β 消除苯氧基离去基团。但是在酮的情况下,2-苯氧基苯乙酮,极化的羰基 π 系统显然直接与富电子的
Catalytic Aerobic Synthesis of Aromatic Ethers from Non-Aromatic Precursors
作者:Marc-Olivier Simon、Simon A. Girard、Chao-Jun Li
DOI:10.1002/anie.201200698
日期:2012.7.23
Only little waste: Aryl ether formation is accomplished by oxidative condensation of alcohols and 2‐cyclohexenones. The reaction complements the existing methods used by synthetic chemists to obtain aryl ethers, and allows a straightforward access to a wide range of functionalized products. In addition, the catalytic reaction with O2 as the oxidant generates water as the only by‐product and provides
Absolute rate constants for the .beta.-scission reaction of the 1-phenyl-2-phenoxypropyl radical: a model for radical reactions of lignin
作者:S. Thomas Autrey、Mikhail S. Alnajjar、David A. Nelson、James A. Franz
DOI:10.1021/jo00006a043
日期:1991.3
Absolute rate expression for beta-scission of the phenoxy radical from the 1-phenyl-2-phenoxypropyl radical, forming cis- and trans-beta-methylstyrene, were determined by competition of beta-scission (k-beta) with abstraction of hydrogen from trimethylstannane (k(abs)). Relative rates (k-beta/k(abs)) were converted to absolute rates (k-beta)) by using a rate expression determined for abstraction of hydrogen atom from tributylstannane by the phenylethyl radical: log [k(abs)/(M-1s-1)] = (9.31 +/- 0.30) - (7.11 +/- 0.49)/theta, where theta = 2.303RT kcal/mol (errors are 2-sigma). The resulting expressions for beta-scission are log (k-beta,(trans)/s-1) = (13.45 +/- 0.26) - (16.94 +/- 0.52)/theta and log (k-beta,(cis)/s-1) = (13.41 +/- 0.3) - (19.3 +/- 0.75)/theta. The basis rate expression for abstraction of hydrogen from tributylstannane by the phenylethyl radical was determined in a competition of abstraction (k(abs) with self-termination (k(t), using the Smoluchowski expression for self-reaction of phenylethyl radical: log [2k(t)/(M-1s-1)] = 11.93 - 3.112/theta. Combining the Arrhenius parameters with the enthalpy change for beta-scission leads to activation barriers for addition of phenoxy radical to trans- and cis-beta-methylstyrene of 5.2 and 6.6 kcal/mol, respectively.
Relative reactivities and stereochemistry for free-radical eliminations of 2-(aryloxy)-1-phenylpropyl radicals
作者:N. Kamrudin Suleman、David A. Nelson
DOI:10.1021/jo00263a050
日期:1989.1
SULEMAN, N. KAMRUDIN;NELSON, DAVID A., J. ORG. CHEM., 54,(1989) N, C. 503-506