93-04-9Relevant articles and documents
Coal. Kinetics of O-Alkylation
Liotta, Ronald,Brons, Glen
, p. 1735 - 1742 (1981)
The kinetic reactivities of the acidic hydroxyl groups in coal were measured.The chemical action of quaternary ammonium hydroxyde bases in the presence of alkylating agents was used as the probe.Both Illinois No. 6 bituminous and Rawhide subbituminous coals contain aromatic and aliphatic hydroxyls as well as lesser amounts of carboxylic acids.Illinois coal was found to O-alkylate at a faster rate than Rawhide coal.The reactivities of the acidic functional groups in the coals were correlated to the reactivity of acidic groups in model compounds.This was accomplished by both relative and absolute kinetic rate measurements on each coal and a series of model systems.It was discovered that the activation energy associated with the nucleophilic displacement determined the rate of O-alkylation of the coal.Therefore, the rate of the reaction is not limited by mass transport of the chemical reagents into the coal structure.In this sense, O-alkylation of coal is a most unique reaction.
C-H Triflation of BINOL Derivatives Using DIH and TfOH
Nakazawa, Hironobu,Sako, Makoto,Masui, Yu,Kurosaki, Ryo,Yamamoto, Shunya,Kamei, Toshiyuki,Shimada, Toyoshi
, p. 6466 - 6470 (2019)
C-H trifluoromethanesulfonyloxylation (triflation) of 1,1′-bi-2-naphthol (BINOL) derivatives has been established under mild conditions using 1,3-diiodo-5,5-dimethylhydantoin (DIH) and trifluoromethanesulfonic acid (TfOH). Up to eight TfO groups can be introduced in a single operation. The resulting highly oxidized BINOL derivatives can be successfully converted to 8,8′-dihydroxy BINOL and bisnaphthoquinone compounds. Mechanistic studies suggested that C-H triflation occurs in the form of an aromatic substitution reaction via the in situ formation of a radical cation.
Methylation with Dimethyl Carbonate/Dimethyl Sulfide Mixtures: An Integrated Process without Addition of Acid/Base and Formation of Residual Salts
Chan, Bun,Lui, Matthew Y.,Lui, Yuen Wai
, (2022/01/08)
Dimethyl sulfide, a major byproduct of the Kraft pulping process, was used as an inexpensive and sustainable catalyst/co-reagent (methyl donor) for various methylations with dimethyl carbonate (as both reagent and solvent), which afforded excellent yields of O-methylated phenols and benzoic acids, and mono-C-methylated arylacetonitriles. Furthermore, these products could be isolated using a remarkably straightforward workup and purification procedure, realized by dimethyl sulfide‘s neutral and distillable nature and the absence of residual salts. The likely mechanisms of these methylations were elucidated using experimental and theoretical methods, which revealed that the key step involves the generation of a highly reactive trimethylsulfonium methylcarbonate intermediate. The phenol methylation process represents a rare example of a Williamson-type reaction that occurs without the addition of a Br?nsted base.
Synthesis of Trinuclear Benzimidazole-Fused Hybrid Scaffolds by Transition Metal-Free Tandem C(sp2)?N Bond Formation under Microwave Irradiation
Dao, Pham Duy Quang,Cho, Chan Sik
, p. 4088 - 4098 (2021/06/16)
2-(2-Bromoaryl)- and 2-(2-bromovinyl)benzimidazoles have been coupled and cyclized with 2-methoxy- and 2-aryloxybenzimidazoles as building blocks in the presence of a base under microwave irradiation to give a class of trinuclear N-fused hybrid scaffolds, benzo[4,5]imidazo[1,2-a]benzo[4,5]imidazo[1,2-c]quinazolines and -pyrimidines, respectively, in good yields. 2-(2-Bromoaryl)- and 2-(2-bromovinyl)imidazoles also reacted with 2-methoxybenzimidazoles in the presence of base under microwave irradiation to give a class of trinuclear N-fused hybrid scaffolds, benzo[4,5]imidazo[1,2-a]imidazo[1,2-c]quinazolines and -pyrimidines, respectively, in similar yields. This process seems to proceed via an initial C(sp2)-N coupling by an addition-elimination nucleophilic aromatic substitution (SNAr) and subsequent cyclization accompanied by extrusion of alcohols.
Ruthenium-Catalyzed Dehydrogenation Through an Intermolecular Hydrogen Atom Transfer Mechanism
Huang, Lin,Bismuto, Alessandro,Rath, Simon A.,Trapp, Nils,Morandi, Bill
supporting information, p. 7290 - 7296 (2021/03/01)
The direct dehydrogenation of alkanes is among the most efficient ways to access valuable alkene products. Although several catalysts have been designed to promote this transformation, they have unfortunately found limited applications in fine chemical synthesis. Here, we report a conceptually novel strategy for the catalytic, intermolecular dehydrogenation of alkanes using a ruthenium catalyst. The combination of a redox-active ligand and a sterically hindered aryl radical intermediate has unleashed this novel strategy. Importantly, mechanistic investigations have been performed to provide a conceptual framework for the further development of this new catalytic dehydrogenation system.