- N-Heterocyclic Carbene/Cobalt Cooperative Catalysis for the Chemo- and Regioselective C?N Bond Formation between Aldehyde and Amines/Amides
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A novel methodology for the construction of various secondary (4 examples), tertiary amides (31 examples), and imides (16 examples) by a Cobalt(II) catalyzed oxidative amide coupling in aqueous media. The Co(III)-TMC was reacted with N-Heteroatom Carbene to form active catalyst Co(II)NHC-TMC in situ which involves in the coordination with Breslow's intermediate and SET for the activation of aldehyde and amides. The mechanism for activation of amide and amine differs on the basis of SET based nucleophilic addition and ligand exchange respectively. The regeneration of the catalyst was achieved using Fe(III)(EDTA)-H2O2 as oxidant. The use of Co(II)TMC-O2 was also found equally efficient in the process. The method is found regioselective for N?H activation in the presence of equally susceptible ortho-C?H bond activation. And amines were found more susceptible then the corresponding amide for the reaction.
- Siddiqui, Asher M.,Khalid, Anam,Khan, Arif,Azad, Chandra S.,Samim, Mohd.,Khan, Imran A.
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p. 4281 - 4287
(2020/07/24)
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- Novel 4- and 7-sulfonylated 2-substituted benzoxazoles
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The efficient synthesis of sulfonylated benzoxazoles at positions C 4 or C7 is reported. The condensation reactions involve original anilide acetal reagents which, upon acid catalysis, allow an easy cyclization reaction with the sulfonylated o-aminophenol partners. This method circumvents the classical use of orthoesters which drawback is the limited access to aromatic reagents. Georg Thieme Verlag Stuttgart.
- Bruyneel, Frédéric,Marchand-Brynaert, Jacqueline
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supporting information; experimental part
p. 1974 - 1978
(2010/10/03)
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- Preparation and study of chemical transformations of N-formyl-N-phenylhydroxylamines
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Nitrosobenzenes with CO2H 1b, CO2CH3 3b and CON(CH3)C6H5 4b ortho-substituents were obtained in a "redox" cell from the corresponding nitro compounds.In order to prepare the 3-oxo-1,2-dihydro-2,1-benzisoxazole-1-carbaldehyde from o-substituted N-formyl-N-phenylhydroxylamines, nitroso derivatives were formylated by glyoxylic acid.The N-formylbenzisoxazolone is unstable in the reaction medium and cannot be isolated.In addition to our study, we showed the unstability of N-formyl-N-phenylhydroxylamines and N-formylanilines in the presence of methanol without acetic acid; in an aqueous methanolic medium, formylation of nitrosoderivatives is equivalent to a reduction of the nitroso group.The mechanism was demonstrated by formylation of the nitrosobenzene and the electrogenerated 2-nitrosobenzene acetic acid 2b.Key Words: flow cell electrosynthesis / nitrosobenzenes / glyoxylic acid / formylation / N-formyl-N-phenylhydroxylamines / N-formylanilines / benzisoxazolones
- Guilbaud-Criqui, A.,Moinet, C.
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p. 164 - 172
(2007/10/02)
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