Photo-triggered hydrogen atom transfer from an iridium hydride complex to unactivated olefins
作者:Mirjam R. Schreier、Björn Pfund、Xingwei Guo、Oliver S. Wenger
DOI:10.1039/d0sc01820a
日期:——
upon photoexcitation, but hydrogen atom transfer (HAT) reactivity is rare. We discovered that a typical representative of a widely used class of iridium hydride complexes acts as an H-atom donor to unactivated olefins upon irradiation at 470 nm in the presence of tertiary alkyl amines as sacrificial electron and proton sources. The catalytic hydrogenation of simple olefins served as a test ground to
许多光敏金属络合物在光激发后可以充当电子给体或受体,但氢原子转移(HAT)反应性很少见。我们发现,在存在叔烷基胺作为牺牲电子和质子源的情况下,在470 nm辐照时,广泛使用的氢化铱配合物类别的典型代表充当未活化烯烃的H原子供体。简单烯烃的催化加氢作为建立氢化铱新光反应性的试验场。通过光致电子转移很难活化的底物很容易被氢化,由12种不同烯烃建立的结构反应性关系与典型的HAT反应性相符,反映了HAT形成的自由基中间体的相对稳定性。激进时钟 H / D同位素标记和瞬态吸收实验提供了进一步的机械原理,并证实了对光触发氢原子转移(photo-HAT)的总体反应性的解释。催化活性物质被鉴定为Ir(II)的氢化物,其Ir II -H键解离自由能约为44 kcal mol -1,这是在对相应的Ir(III)氢化物进行3 MLCT激发态淬灭后形成的,即实际的HAT步骤发生在地面上-状态势能面。本文介绍的ph
Harnessing Applied Potential: Selective β-Hydrocarboxylation of Substituted Olefins
作者:Anas Alkayal、Volodymyr Tabas、Stephanie Montanaro、Iain A. Wright、Andrei V. Malkov、Benjamin R. Buckley
DOI:10.1021/jacs.9b13305
日期:2020.1.29
The construction of carboxylic acid compounds in a selective fashion from low value materials such as alkenes remains a long-standing challenge to synthetic chemists. In particular, β-addition to styrenes is underdeveloped. Herein we report a new electrosynthetic approach to the selective hydrocarboxylation of alkenes that overcomes the limitations of current transition metal and photochemical approaches
(HAT). Synthetically useful deuterium-labelled compounds can be straightforwardly obtained by replacing H2O with D2O. Moreover, the dual photocatalytic system and the photocatalytic conditions can be rationally designed to tune the selectivity for aryl olefin vs. aryl ketone reduction; not only by changing the structural and electronic properties of the cobalt catalysts, but also by modifying the reduction
报道了一种基于地球丰富元素的催化体系,该体系使用可见光作为驱动力,H 2 O 作为唯一的氢原子源,有效地氢化芳基烯烃。该催化系统涉及稳健且定义明确的氨基吡啶钴络合物和杂配Cu光氧化还原催化剂。该系统以显着的选择性 (>20 000)与水还原 (WR) 相比,显示了水介质中苯乙烯的还原。反应性和机理研究支持形成 [Co-H] 中间体,该中间体通过氢原子转移 (HAT) 与烯烃反应。可以通过用 D 2代替 H 2 O直接获得合成有用的氘标记化合物O. 此外,可以合理设计双光催化系统和光催化条件,以调整芳基烯烃与芳基酮还原的选择性;不仅通过改变钴催化剂的结构和电子特性,还通过改变光氧化还原催化剂的还原特性。
Carbonyl cross-metathesis via deoxygenative gem-di-metal catalysis
作者:Lumin Zhang、David A. Nagib
DOI:10.1038/s41557-023-01333-8
日期:2024.1
Carbonyls and alkenes are versatile functional groups, whose reactivities are cornerstones of organic synthesis. The selective combination of two carbonyls to form an alkene—a carbonyl cross-metathesis—would be a valuable tool for their exchange. Yet, this important synthetic challenge remains unsolved. Although alkene/alkene and alkene/carbonyl cross-metathesisreactions are known, there is a lack
Reactions of diphenylphosphinoyl radicals with 5-aryl-2-pentenoates or beta-phenylethylene styrenes generate trans-substituted tetrahydronaphthalenes through a cascade reaction sequence.