scholarly journals Mechanistic investigations of a bifunctional squaramide organocatalyst in asymmetric Michael reaction and observation of stereoselective retro-Michael reaction

RSC Advances ◽  
2015 ◽  
Vol 5 (115) ◽  
pp. 95079-95086 ◽  
Author(s):  
Eszter Varga ◽  
László Tamás Mika ◽  
Antal Csámpai ◽  
Tamás Holczbauer ◽  
György Kardos ◽  
...  
Keyword(s):  
Kinetic Parameters ◽  
Michael Addition ◽  
Michael Reaction ◽  
Mechanistic Investigations ◽  
Asymmetric Michael Reaction

The mechanism of cinchona–squaramide organocatalytic Michael addition was studied usingin situIR and NMR experiments. As a result, not only kinetic parameters were determined but a stereoselective retro-Michael reaction was also observed.

Direct organocatalytic asymmetric Michael reaction of fluorine hemiaminal-type nucleophile to 4-nitro-5-styrylisoxazoles

2020 ◽  
Vol 7 (11) ◽  
pp. 1343-1348
Author(s):  
Luyao Li ◽  
Bo Zhu ◽  
Huihui Fan ◽  
Zhiyong Jiang ◽  
Junbiao Chang
Keyword(s):  
Michael Addition ◽  
Michael Reaction ◽  
Addition Reaction ◽  
Michael Addition Reaction ◽  
Asymmetric Michael Addition ◽  
Asymmetric Michael Reaction ◽  
First Time

Herein, we report a chiral bifunctional thiourea catalyzed asymmetric Michael addition reaction between 2-(trifluoromethyl)oxazol-5(2H)-one as a direct C-2-position nucleophile to 4-nitro-5-styrylisoxazoles for the first time.

Organocatalytic asymmetric Michael addition of 1-acetylcyclohexene and 1-acetylcyclopentene to nitroolefins

2015 ◽  
Vol 13 (25) ◽  
pp. 7076-7083 ◽  
Author(s):  
Utpal Nath ◽  
Ankush Banerjee ◽  
Bidhan Ghosh ◽  
Subhas Chandra Pan
Keyword(s):  
Michael Addition ◽  
Michael Reaction ◽  
Primary Amines ◽  
Asymmetric Michael Addition ◽  
Asymmetric Michael Reaction

The first organocatalytic asymmetric Michael reaction between α-branched enones namely 1-acetylcyclohexene, 1-acetylcyclopentene and 1-acetylcyclobutene with nitroolefins has been developed using primary amines as catalysts.

Absolute Konfiguration von (+)-1,2,3,4,6,7,8,8a-Octahydro-6-isochinolon- 8a-carbonsäuremethylester und die Stereochemie einer Kupfer-katalysierten asymmetrischen Michael-Reaktion / Absolute Configuration of Methyl (+)-1,2,3,4,6,7,8,8a-Octahydro-6-isoquinolone-8a-carboxylate and Stereochemistry of a Copper-Catalyzed Asymmetric Michael Reaction

2004 ◽  
Vol 59 (4) ◽  
pp. 375-379 ◽  
Author(s):  
Jens Christoffers ◽  
Wolfgang Frey ◽  
Heiko Scharl ◽  
Angelika Baro
Keyword(s):  
Absolute Configuration ◽  
Michael Addition ◽  
Michael Reaction ◽  
Addition Product ◽  
Crystallographic Analysis ◽  
Subsequent Reaction ◽  
X Ray ◽  
Quaternary Stereocenter ◽  
Asymmetric Michael Reaction

AbstractEnantiopure Boc-protected piperidine derivative (+)-5c, with a quaternary stereocenter, was obtained by copper-catalyzed, L-valine diethylamide-mediated Michael reaction. For determination of the absolute configuration, 5c was derivatized by cyclization with pyrrolidine/AcOH to give compound 6 with bicyclo[4.4.0]-constitution, deprotection of the amino function with TFA and subsequent reaction with 2-iodobenzoic acid to yield the crystalline bicyclic amide 7. X-ray crystallographic analysis confirmed the constitution of compounds 5c and 6 and established the (R) configuration of 7. Thus, starting Michael addition product (+)-5c has to be (S) configured, because an epimerization at the quaternary stereocenter is excluded. This result is in accordance with our working model of the Cu-catalyzed, auxiliary-assisted Michael reaction.

ChemInform Abstract: Tandem Asymmetric Michael Reaction-Intramolecular Michael Addition. An Easy Entry to Chiral Fluorinated 1,4-Dihydropyridines.

ChemInform ◽  
2010 ◽  
Vol 41 (48) ◽  
pp. no-no
Author(s):  
Santos Fustero ◽  
Silvia Catalan ◽  
Maria Sanchez-Rosello ◽  
Antonio Simon-Fuentes ◽  
Carlos del Pozo
Keyword(s):  
Michael Addition ◽  
Michael Reaction ◽  
Asymmetric Michael Reaction

scholarly journals Synthesis of non-racemic 4-nitro-2-sulfonylbutan-1-ones via Ni(II)-catalyzed asymmetric Michael reaction of β-ketosulfones

2019 ◽  
Vol 15 ◽  
pp. 1289-1297 ◽  
Author(s):  
Alexander N Reznikov ◽  
Anastasiya E Sibiryakova ◽  
Marat R Baimuratov ◽  
Eugene V Golovin ◽  
Victor B Rybakov ◽  
...  
Keyword(s):  
Organic Synthesis ◽  
Bioactive Compounds ◽  
Michael Addition ◽  
Michael Reaction ◽  
High Yield ◽  
Michael Adducts ◽  
Significant Rate ◽  
Asymmetric Michael Addition ◽  
Stereogenic Centers ◽  
Asymmetric Michael Reaction

Functionally substituted sulfones with stereogenic centers are valuable reagents in organic synthesis and key motifs in some bioactive compounds. The asymmetric Michael addition of β-ketosulfones to conjugated nitroalkenes in the presence of Ni(II) complexes with various chiral vicinal diamines was studied. This reaction provides convenient access to non-racemic 4-nitro-2-sulfonylbutan-1-ones with two stereocenters with high yield and excellent enantioselectivity (up to 99%). It has been established that the catalytic Michael reaction itself was carried out with high diastereoselectivity, but the Michael adducts may epimerize at the C-2 position at a significant rate. Conditions for the preparation of individual diastereomers were found.

Tandem Asymmetric Michael Reaction−Intramolecular Michael Addition. An Easy Entry to Chiral Fluorinated 1,4-Dihydropyridines

2010 ◽  
Vol 12 (15) ◽  
pp. 3484-3487 ◽  
Author(s):  
Santos Fustero ◽  
Silvia Catalán ◽  
María Sánchez-Roselló ◽  
Antonio Simón-Fuentes ◽  
Carlos del Pozo
Keyword(s):  
Michael Addition ◽  
Michael Reaction ◽  
Asymmetric Michael Reaction

scholarly journals Microbial N2O consumption in and above marine N2O production hotspots

2020 ◽  
Author(s):  
Xin Sun ◽  
Amal Jayakumar ◽  
John C. Tracey ◽  
Elizabeth Wallace ◽  
Colette L. Kelly ◽  
...  
Keyword(s):  
Kinetic Parameters ◽  
Substrate Affinity ◽  
N2o Production ◽  
Anoxic Waters ◽  
Production And Consumption ◽  
Consumption Rates ◽  
Anoxic Zones ◽  
First Time ◽  
Microbial N

AbstractThe ocean is a net source of N2O, a potent greenhouse gas and ozone-depleting agent. However, the removal of N2O via microbial N2O consumption is poorly constrained and rate measurements have been restricted to anoxic waters. Here we expand N2O consumption measurements from anoxic zones to the sharp oxygen gradient above them, and experimentally determine kinetic parameters in both oxic and anoxic seawater for the first time. We find that the substrate affinity, O2 tolerance, and community composition of N2O-consuming microbes in oxic waters differ from those in the underlying anoxic layers. Kinetic parameters determined here are used to model in situ N2O production and consumption rates. Estimated in situ rates differ from measured rates, confirming the necessity to consider kinetics when predicting N2O cycling. Microbes from the oxic layer consume N2O under anoxic conditions at a much faster rate than microbes from anoxic zones. These experimental results are in keeping with model results which indicate that N2O consumption likely takes place above the oxygen deficient zone (ODZ). Thus, the dynamic layer with steep O2 and N2O gradients right above the ODZ is a previously ignored potential gatekeeper of N2O and should be accounted for in the marine N2O budget.

ChemInform Abstract: High Diastereoselectivity Induced by a Fluorous Alkyl Group in the Asymmetric Michael Reaction of Nitroalkenes Catalyzed by a Prolinol Methyl Ether.

ChemInform ◽  
2014 ◽  
Vol 45 (18) ◽  
pp. no-no
Author(s):  
Kazumasa Funabiki ◽  
Masaya Ohta ◽  
Yuta Sakaida ◽  
Kiyofumi Oida ◽  
Yasuhiro Kubota ◽  
...  
Keyword(s):  
Methyl Ether ◽  
Alkyl Group ◽  
Michael Reaction ◽  
Asymmetric Michael Reaction
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