4013-34-7Relevant articles and documents
Regioselective N-Functionalization of Tautomerizable Heterocycles through Methyl Trifluoromethanesulfonate-Catalyzed Substitution of Alcohols and Alkyl Group Migrations
Biswas, Srijit,Biswas, Subrata,Duari, Surajit,Elsharif, Asma M.,Maity, Srabani,Mishra, Abhishek Kumar,Morgon, Nelson H.,Roy, Arnab,de Souza, Aguinaldo R.
, (2022/01/20)
A catalytic synthetic strategy has been developed combining two protocols, such as, direct nucleophilic substitution of alcohols followed by X- to N- alkyl group migration (X=O, S) to access N-functionalized benzoxazolones, benzothiazolethiones, indolinone, benzoimidazolethiones, and pyridinones derivatives. Methyl trifluoromethanesulfonate (MeOTf) was found to catalyze the reaction, which revealed the catalytic property of MeOTf. A mechanism was established through experiments as well as DFT calculations wherein the ?OH group of alcohols were converted to the corresponding ?OMe groups and in situ generated TfOH. The ?OMe groups produced underwent TfOH catalyzed ?X alkylation (X=O, S) of the heterocycles followed by ?X- to ?N-alkyl group migrations in a single step. (Figure presented.).
Multiple Mechanisms Mapped in Aryl Alkyl Ether Cleavage via Aqueous Electrocatalytic Hydrogenation over Skeletal Nickel
Hegg, Eric L.,Jackson, James E.,Klinger, Grace E.,Saffron, Christopher M.,Zhou, Yuting
supporting information, p. 4037 - 4050 (2020/03/10)
We present here detailed mechanistic studies of electrocatalytic hydrogenation (ECH) in aqueous solution over skeletal nickel cathodes to probe the various paths of reductive catalytic C-O bond cleavage among functionalized aryl ethers relevant to energy science. Heterogeneous catalytic hydrogenolysis of aryl ethers is important both in hydrodeoxygenation of fossil fuels and in upgrading of lignin from biomass. The presence or absence of simple functionalities such as carbonyl, hydroxyl, methyl, or methoxyl groups is known to cause dramatic shifts in reactivity and cleavage selectivity between sp3 C-O and sp2 C-O bonds. Specifically, reported hydrogenolysis studies with Ni and other catalysts have hinted at different cleavage mechanisms for the C-O ether bonds in α-keto and α-hydroxy β-O-4 type aryl ether linkages of lignin. Our new rate, selectivity, and isotopic labeling results from ECH reactions confirm that these aryl ethers undergo C-O cleavage via distinct paths. For the simple 2-phenoxy-1-phenylethane or its alcohol congener, 2-phenoxy-1-phenylethanol, the benzylic site is activated via Ni C-H insertion, followed by beta elimination of the phenoxide leaving group. But in the case of the ketone, 2-phenoxyacetophenone, the polarized carbonyl πsystem apparently binds directly with the electron rich Ni cathode surface without breaking the aromaticity of the neighboring phenyl ring, leading to rapid cleavage. Substituent steric and electronic perturbations across a broad range of β-O-4 type ethers create a hierarchy of cleavage rates that supports these mechanistic ideas while offering guidance to allow rational design of the catalytic method. On the basis of the new insights, the usage of cosolvent acetone is shown to enable control of product selectivity.
Oxidation of Secondary Methyl Ethers to Ketones
Gilissen, Pieter J.,Blanco-Ania, Daniel,Rutjes, Floris P. J. T.
supporting information, p. 6671 - 6679 (2017/07/15)
We present a mild way of converting secondary methyl ethers into ketones using calcium hypochlorite in aqueous acetonitrile with acetic acid as activator. The reaction is compatible with various oxygen- and nitrogen-containing functional groups and afforded the corresponding ketones in up to 98% yield. The use of this methodology could expand the application of the methyl group as a useful protecting group.