30825-55-9Relevant articles and documents
Imidazole derivatives as accelerators for ruthenium-catalyzed hydroesterification and hydrocarbamoylation of alkenes: Extensive ligand screening and mechanistic study
Konishi, Hideyuki,Muto, Takashi,Ueda, Tsuyoshi,Yamada, Yayoi,Yamaguchi, Miyuki,Manabe, Kei
, p. 836 - 845 (2015/03/14)
Imidazole derivatives are effective ligands for promoting the [Ru3(CO)12]-catalyzed hydroesterification of alkenes using formates. Extensive ligand screening was performed to identify 2-hydroxymethylated imidazole as the optimal ligand. Neither carbon monoxide gas nor a directing group was required, and the reaction also showed a wide substrate generality. The Ru-imidazole catalyst system also promoted intramolecular hydrocarbamoylation to afford lactams. A Ru-imidazole complex was unambiguously analyzed by X-ray crystallography, and it had a trinuclear structure derived from one [Ru3(CO)12] and two ligands. This complex was also successfully used for hydroesterification. The mechanism was examined in detail by using D- and 13C-labeled formates, indicating that the hydroesterification reaction proceeds by a decarbonylation-recarbonylation pathway. Effective imidazole assistant: [Ru3(CO)12]-catalyzed hydroesterification of alkenes by using formates is drastically accelerated by imidazole derivatives and exhibits a broad substrate scope for both alkenes and formates. The Ru-imidazole complex also catalyzes the intramolecular hydrocarbamoylation of alkenes.
Synthesis of Chiral 3-Alkyl-3,4-dihydroisocoumarins by dynamic kinetic resolutions catalyzed by a Baeyer-Villiger Monooxygenase
Rioz-Martinez, Ana,De Gonzalo,Torres Pazmino, Daniel E.,Fraaije, Marco-W.,Gotor, Vicente
supporting information; experimental part, p. 2073 - 2076 (2010/06/17)
"Chemical Equation Presented" Baeyer-Villiger monooxygenases have been tested, in the oxidation of racemic benzofused ketones. When employing a single mutant of phenylacetone monooxygenase (M.446G PAMO) under the proper reaction conditions, it was possible to achieve 3-substituted 3,4-dihydroisocoumarins with, high yields and optical purities through regioselective dynamic kinetic resolution processes.
Enantioselective cathodic reduction of 4-methylcoumarin: Dependence of selectivity on reaction conditions and investigation of the mechanism
Nielsen, Merete Folmer,Batanero, Belen,Loehl, Thorsten,Schaefer, Hans J.,Wuerthwein, Ernst-Ulrich,Froehlich, Roland
, p. 2011 - 2024 (2007/10/03)
The cathodic reduction of 4-methylcoumarin (1) in acidic methanol/water in the presence of yohimbine leads to formation of a mixture of the hydrogenation product 4-methyl-3,4-dihydrocoumarin (2), with an enantiomeric excess (ee) of (R)-2 of 0-67%, and the hydrodimer 3. The relative yields of 2 and 3 and the ee of 2 depend on a number of experimental parameters such as pH, supporting electrolyte, working potential, and the concentrations of substrate and yohimbine, as demonstrated by a series of preparative-scale experiments. In addition, a series of voltammetric and kinetic measurements were carried out to investigate the influence of the individual experimental parameters. Three mechanistic possibilities have been examined, and by combination of the analytical data with the results of the preparative experiments, a single model is put forward which is in accord with the available results. The main features of the mechanistic model can be summarized as follows: 1) under acidic conditions (pH 2-3) the electroactive species is a complex between 1 and H3O+, the reduction of which leads to an enolic radical; 2) this radical is not reduced at the working potential but tautomerizes into the more easily reduced keto radical or dimerizes; 3) the keto radical is reduced and further protonated; 4) the function of the yohimbineH+ is to catalyze the tautomerization and enantioselectively protonate the final carbanion. Additionally, we conclude that the concentration of yohimbine in the immediate vicinity of the electrode is considerably higher than its stoichiometric concentration. Quantum chemical calculations demonstrate that si protonation of the intermediate anion by yohimbineH+ to give (R)-2 is energetically favored.
