cobaloxime to produce olefins and H2. This operationally simple method enables direct dehydrogenation of readily available chemical feedstocks to diversely functionalized olefins. For example, we demonstrate, for the first time, the oxidant-free desaturation of thioethers and amides to alkenyl sulfides and enamides, respectively. Moreover, the system’s exceptional siteselectivity and functional group
脂肪族催化脱氢 (CDA) 在有机合成中的价值在很大程度上仍未得到充分探索。已知的均相 CDA 系统通常需要使用牺牲氢受体(或氧化剂)、贵金属催化剂和苛刻的反应条件,因此将大多数现有方法限制为非或低官能化烷烃的脱氢。在这里,我们描述了一种可见光驱动的双催化剂系统,该系统由廉价的有机光氧化还原和贱金属催化剂组成,用于室温、无受体 CDA (Al-CDA)。该过程由光激发的 2-氯蒽醌引发,涉及脂肪族的 H 原子转移 (HAT) 形成烷基自由基,然后与钴肟反应生成烯烃和 H 2. 这种操作简单的方法能够将容易获得的化学原料直接脱氢成多种官能化的烯烃。例如,我们首次证明了硫醚和酰胺在无氧化剂条件下分别脱饱和为烯基硫醚和烯酰胺。此外,14 种生物相关分子和药物成分的后期脱氢和合成说明了该系统卓越的位点选择性和官能团耐受性。机理研究揭示了双重 HAT 过程,并提供了对反应性和位点选择性起源的见解。
Diarylrhodates as Promising Active Catalysts for the Arylation of Vinyl Ethers with Grignard Reagents
with 2 equiv of aryl Grignardreagents, were found to be effective active catalysts in cross-coupling reactions of vinyl ethers with aryl Grignardreagents, giving rise to the production of vinyl arenes. In this catalytic system, vinyl-O bonds were preferably cleaved over Ar-O or Ar-Br bonds. A lithium rhodate complex was isolated, and its crystalstructure was determined by X-ray crystallography.
通过 [RhCl(cod)]2 与 2 当量的芳基格氏试剂反应生成的阴离子二芳基铑配合物被发现是乙烯基醚与芳基格氏试剂交叉偶联反应的有效活性催化剂,从而产生乙烯基芳烃. 在该催化系统中,乙烯基-O键优选在Ar-O或Ar-Br键上裂解。分离出一种铑酸锂络合物,并通过 X 射线晶体学确定其晶体结构。
Catalytic Dehydrogenation of<i>o</i>-Alkylated or<i>o</i>-Alkoxylated Iodoarenes with Concomitant Hydrogenolysis
作者:Elena Motti、Marta Catellani
DOI:10.1002/adsc.200700562
日期:2008.3.7
Palladium-catalyzed dehydrogenation of suitable chains bonded to an ortho position of an iodoarene has been achieved by two methods both involving oxidative addition of the iodoarene to palladium(0) and palladacycle formation under mild conditions.
a solvent and an interaction partner. This protocol also features broad substrate scope, excellent functional group compatibility, and mild reaction conditions without transition metals. Moreover, the gram-scale synthesis of olefins and the generation of pharmaceutical intermediates highlighted its practical applicability. Lastly, mechanistic studies indicate that the reaction was initiated via noncovalent
Pyrolysis of azetidinone derivatives: a versatile route towards electron-rich alkenes, C-1 allylation and/or homologation of aldehydes
作者:Nouf S. Al-Hamdan、Osama M. Habib、Yehia A. Ibrahim、Nouria A. Al-Awadi、Osman M. E. El-Dusouqui
DOI:10.1039/c4ra01024h
日期:——
β-thiolactams led essentially to stereoselective synthesis of the high energy electron-rich Z-alkenes. Extension of this methodology to the pyrolysis of 3-allyloxy derivatives gave a simple direct route to the synthetically important 4-pentenal. These pyrolytic transformations convert aldehydes to aryloxyalkenes (a protected homologation) and 4-pentenal (a C-1 allylation and homologation). The starting