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101.
Base‐Free Conditions for Rhodium‐Catalyzed Asymmetric Arylation To Produce Stereochemically Labile α‐Aryl Ketones
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Dr. Xiaowei Dou Prof. Dr. Yixin Lu Prof. Dr. Tamio Hayashi 《Angewandte Chemie (International ed. in English)》2016,55(23):6739-6743
The asymmetric arylation of 2,2‐dialkyl cyclopent‐4‐ene‐1,3‐diones with aryl boronic acids was found to be efficiently catalyzed by a chiral diene–rhodium μ‐chloro dimer, [{RhCl((R)‐diene*)}2], in the absence of bases in toluene/H2O to give 2,2‐dialkyl 4‐aryl cyclopentane‐1,3‐diones in high yields with high enantioselectivity. Such compounds can not be obtained with high enantiomeric purity under the standard basic conditions used for rhodium‐catalyzed asymmetric arylation because the α‐aryl ketone products undergo racemization under the basic conditions. 相似文献
102.
A palladium-catalyzed intermolecular cycloaddition of gamma-methylidene-delta-valerolactones with electron-deficient olefins has been developed for the synthesis of spiro[2.4]heptanes with high selectivity through a nucleophilic ring closure to the central carbon of a pi-allylpalladium intermediate. It was found that the course of the reaction is dependent on the ligand employed, and selective [4 + 2] cycloadditions can also be achieved by the use of a bulky monophosphine ligand. 相似文献
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104.
Addition of arylmagnesium bromides to aryl(alkyl)acetylenes proceeded in the presence of an iron catalyst and a N-heterocyclic carbene ligand to give high yields of the corresponding alkenylmagnesium reagents, which were transformed into tetrasubstituted alkenes by subsequent treatment with electrophiles. [reaction: see text] 相似文献
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107.
FeCl(3) in combination with t-BuOOt-Bu as an oxidant was found to be an efficient catalyst for oxidation of alkylamides to α-(tert-butoxy)alkylamides. FeCl(2) and CuCl showed, respectively, almost the same and slightly lower activities compared with FeCl(3) in the tert-butoxylation of N-phenylpyrrolidone (1a), whereas no tert-butoxylated product was obtained by use of Fe(OTf)(3), RuCl(3), or Zr(OTf)(4). FeCl(3) was found to be effective also as a catalyst for the Friedel-Crafts alkylation with thus obtained α-(tert-butoxy)alkylamides. The Friedel-Crafts alkylation proceeded smoothly also in the presence of a catalytic amount of Fe(OTf)(3), RuCl(3), or Zr(OTf)(4). In contrast, FeCl(2) and CuCl, which showed certain activity toward the tert-butoxylation, failed to promote the Friedel-Crafts alkylation. Among the transition metal complexes thus far examined, only FeCl(3) showed high catalytic activities for both the oxidation and the Friedel-Crafts alkylation. The bifunctionality of FeCl(3) was utilized for the oxidative coupling of alkylamides with arenes through a tandem reaction consisting of oxidation of alkylamides to α-(tert-butoxy)alkylamides and the following Friedel-Crafts alkylation. The FeCl(3)-catalyzed oxidative coupling is applicable to a wide variety of alkylamides and arenes, though a combination of FeCl(3) with Fe(OTf)(3) was found to be effective for the reaction of arenes with low nucleophilicity. A Fe(II)-Fe(III) catalytic cycle is concerned with the tert-butoxylation, whereas a Fe(III) complex as a Lewis acid catalyzes the Friedel-Crafts alkylation. 相似文献
108.
A palladium-catalyzed formal [6 + 3] cyclization of γ-methylidene-δ-valerolactones with aziridines has been developed to produce 1,4-oxazonan-9-ones, a class of nine-membered azlactones that are not easily accessible by existing methods. The products thus obtained can also be further functionalized with ease. 相似文献
109.
R Shintani T Ito M Nagamoto H Otomo T Hayashi 《Chemical communications (Cambridge, England)》2012,48(79):9936-9938
A palladium-catalyzed asymmetric synthesis of 2-pyrrolidinones with a quaternary stereocenter at the 3-position has been achieved by the reaction of γ-methylidene-δ-valerolactones with alkyl isocyanates. High enantioselectivity has been realized by employing a newly synthesized chiral phosphoramidite ligand. 相似文献
110.
S. Lakshmi Reddy K.N.M. Reddy G. Siva Reddy Tamio Endo R.L. Frost 《Molecular physics》2013,111(11):1467-1470
Mottramite mineral from Tsumeb Corporation Mine, Tsumeb, Otavi, Namibia, is investigated in this present work. The mineral contains vanadium and copper contents of 22.73% and 16.84% by weight, respectively, as V2O5 and CuO. An electron paramagnetic resonance (EPR) study confirmed the presence of Cu(II) with g = 2.2. The optical absorption spectrum of mottramite indicates that Cu(II) is present in a rhombic environment. Near infrared results are due to water fundamentals. 相似文献