29335-87-3Relevant articles and documents
Direct aerobic oxidation of 2-benzylpyridines in a gas-liquid continuous-flow regime using propylene carbonate as a solvent
Pieber, Bartholomaeus,Kappe, C. Oliver
, p. 320 - 324 (2013)
The use of high-temperature/pressure gas-liquid continuous flow conditions dramatically enhances the iron-catalyzed aerobic oxidation of 2-benzylpyridines to their corresponding ketones. Pressurized air serves as a readily available oxygen source and propylene carbonate as a green solvent in this radically intensified preparation of synthetically valuable 2-aroylpyridines.
Heteroleptic Ni(II) Complexes Bearing a Bulky Yet Flexible IBiox-6 Ligand: Improved Selectivity in Cross-Electrophile Coupling of Benzyl Chlorides with Aryl Chlorides/Fluorides
Shen, Zheng-Wang,Meng, Die-Die,Imran, Sajid,Yan, Chun-Hui,Sun, Hong-Mei
supporting information, p. 3540 - 3545 (2020/10/09)
A bisoxazoline-derived NHC known as IBiox-6 reacted smoothly with Ni[P(OEt)3]2Br2 and Ni(PPh3)2Br2 to give the respective heteroleptic Ni(II) complexes Ni(IBiox-6)[P(OEt)3]Br2 (1) and Ni(IBiox-6)(PPh3)Br2 (2) in yields of 60% and 71%. Their crystal structures were characterized to reveal a rare cis disposition of the IBiox-6 ligand to the phosphite ligand in 1, while 2 possessed the more common trans configuration. Both complexes catalyzed the cross-electrophile coupling of benzyl chlorides with aryl chlorides and fluorides in the presence of Mg turnings at 50 °C via a "real one-pot"procedure, featuring no requirement for temperature variation or portionwise addition of any coupling partner. In particular, complex 1 showed a better balance between the catalytic activity and selectivity. The scope of the procedure catalyzed by 1 and Mg turnings was investigated, providing a highly selective, simple, and practical approach to the synthesis of diarylmethanes with high steric hindrance and various functional groups, including oligo-diarylmethane with asymmetric structures.
Metal-Free Halogen(I) Catalysts for the Oxidation of Aryl(heteroaryl)methanes to Ketones or Esters: Selectivity Control by Halogen Bonding
Guha, Somraj,Sekar, Govindasamy
supporting information, p. 14171 - 14182 (2018/09/10)
Metal-free halogen(I) catalysts were used for the selective oxidation of aryl(heteroaryl)methanes [C(sp3)?H] to ketones [C(sp2)=O] or esters [C(sp3)?O]. The synthesis of ketones was performed with a catalytic amount of NBS in DMSO solvent. Experimental studies and density functional theory (DFT) calculations supported the formation of halogen bonding (XB) between the heteroarene and N-bromosuccinimide, which enabled imine–enamine tautomerism of the substrates. No additional activator was required for this crucial step. Isotope-labeling and other supporting experiments suggested that a Kornblum-type oxidation with DMSO and aerobic oxygenation with molecular oxygen took place simultaneously. A background XB-assisted electron transfer between the heteroarenes and halogen(I) catalysts was responsible for the formation of heterobenzylic radicals and, thus, the aerobic oxygenation. For selective acyloxylation (ester formation), a catalytic amount of iodine was employed with tert-butyl hydroperoxide in aliphatic carboxylic acid solvent. Several control reactions, spectroscopic studies, and Time-Dependent Density Functional Theory (TD–DFT) calculations established the presence of acetyl hypoiodite as an active halogen(I) species in the acetoxylation process. With the help of a selectivity study, for the first time we report that the strength of the XB interaction and the frontier orbital mixing between the substrates and acyl hypoiodites determined the extent of the background electron-transfer process and, thus, the selectivity of the reaction.
