Decatungstate As Photoredox Catalyst: Benzylation of Electron-Poor Olefins
摘要:
Excited tetrabutylammonium decatungstate (TBADT), known to activate a variety of compounds via hydrogen atom transfer (HAT), has now been applied as a photoredox catalyst for the effective oxidative cleavage of benzyl silanes and radical benzylation of reducible olefins occurring in isolated yields from poor to excellent.
Dimeric Metal Complexes as Mediators for Radical C?C Bond-Forming Reactions
作者:Bernd Giese、Gebhard Thoma
DOI:10.1002/hlca.19910740523
日期:1991.8.7
(2) in the presence of alkyl halides leads to C-centered radicals which can be trappedby alkenes and yields saturated and/or unsaturated addition products. Carbon radicals are generated via halogen abstraction by the initially formed metal-centered radicals resulting from homolysis of the metal-metal bond of dimericmediators 1 and 2. No reaction occurs using octacarbonyldicobalt (3).
of alkyl and acyl radicals onto electron-poor olefins or diisopropyl azodicarboxylate has been carried out on a multi-gram scale under continuous flow conditions. The process is based on the use of the inorganic photocatalyst tetrabutylammonium decatungstate (TBADT), which is capable to activate selectively a variety of CH bonds in different substrates, including aldehydes, amides, ethers and alkanes
已经在连续流动条件下以克为单位进行了一组烷基和酰基自由基在贫电子烯烃或偶氮二羧酸二异丙酯上的原子经济自由基共轭加成反应。该方法基于使用无机光催化剂四丁基癸二酸铵(TBADT),它能够选择性地活化不同底物(包括醛,酰胺,醚和烷烃)中的多种CH键。根据该程序已经合成了广泛的合成靶,包括1,4-双官能化的衍生物(例如1,4-二酮或酮酯)。所有反应均在中观条件下进行规模的流量光反应器,包括缠绕在水冷500 W中压汞蒸气灯周围的紫外线透明FEP管(氟化乙烯丙烯)的盘管。这种光化学设备的使用导致了停留时间的减少,相对于相应的批处理过程所测得的停留时间而言,STY(时空产率)和生产率值显着提高,通常会导致整体效率的提高。过程的可持续性(过程质量强度– PMI –值低至10 kg kg -1)。
C?C Bond Formationvia Carbon-Centered Radicals Generated from Dicarbonyl(?5-cyclopentadienyl) organoiron Complexes
作者:Bernd Giese、Gebhard Thoma
DOI:10.1002/hlca.19910740524
日期:1991.8.7
benzyldicarbonyl(η5-cyclopentadienyl)iron complex (2) leads to hemolytic cleavage of the FeC bond. In the presence of activated alkenes, radical addition occurs and both saturated and unsaturated addition products 7–9 are formed. Photolysis of alkyliron complexes 2,3 and 20 in the presence of acrylonitrile leads to the same products as the irradiation of the respective acyliron complexes 28–30. This indicates that
Arylacetic acids were used as sources of benzyl radicals under tetrabutylammonium decatungstatephotocatalyzed conditions for the benzylation of electron-poor olefins. The reaction proceeds smoothly in a mixed aqueous medium (MeCN/H2O 2/1) in the presence of NaHCO3, NaClO4, and an electron transfer agent (biphenyl). The reaction tolerates a wide variety of functional groups on the aromatic ring (whether
在四丁基铵去癸酸盐光催化条件下,丙烯酸被用作苄基的来源,用于贫电子烯烃的苄基化。在NaHCO 3,NaClO 4和电子转移剂(联苯)的存在下,反应在混合水性介质(MeCN / H 2 O 2/1)中平稳进行。该反应可耐受芳环上的各种官能团(无论是供电子还是吸电子),并可扩展为杂芳族类似物。烯烃具有自由基陷阱和电子受体的双重作用。本方法还可扩展至芳基丙酸(包括非甾体抗炎药布洛芬和氟比洛芬),以及扁桃酸衍生物。
Control of Site-Selectivity in Hydrogen Atom Transfer by Electrostatic Interaction: Proximal-Selective C(sp<sup>3</sup>)–H Alkylation of 2-Methylanilinium Salts Using a Decatungstate Photocatalyst
作者:Jialin Zeng、Takeru Torigoe、Yoichiro Kuninobu
DOI:10.1021/acscatal.2c00278
日期:2022.3.4
C(sp3)–H alkylation of 2-methylanilinium saltsvia radical intermediates was developed. The anionic decatungstate photocatalyst ([W10O32]4–) interacts with the ammonium group of the substrate through electrostatic interaction and selectively abstracts a hydrogen atom from the proximal benzylic carbon atom under UV irradiation. A variety of 2-methylanilinium salts reacted with electron-deficient alkenes
开发了通过自由基中间体对 2-甲基苯胺盐进行位点选择性 C(sp 3 )-H 烷基化。阴离子十钨酸盐光催化剂([W 10 O 32 ] 4-)通过静电相互作用与底物的铵基相互作用,并在紫外线照射下选择性地从近端苄基碳原子中提取一个氢原子。多种 2-甲基苯胺盐与缺电子烯烃反应。烷基化产物通过 C-N 键的断裂成功地转化为芳基碘化物,并通过分子内环化成功地转化为四氢苯并氮杂酮衍生物。机理研究清楚地表明 [W 10 O 32 ] 4–和铵基。