michael acceptors
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2022 ◽  
Author(s):  
Mateusz Dyguda ◽  
Anna Skrzyńska ◽  
Lesław Sieroń ◽  
Łukasz Albrecht

In the manuscript the first enantioselective dearomative Michael addition between α,β-unsaturated aldehydes and 2-nitrobenzofurans realized under N-heterocyclic carbene activation has been described. The reaction proceeds via addition of homoenolate to Michael acceptors leading to the formation of biologically important heterocycles with high yields and stereoselectivities. Their functionalization potential has been confirmed in selected, diastereoselective transformations.


Author(s):  
Miran Lemmerer ◽  
Margaux Riomet ◽  
Ricardo Meyrelles ◽  
Boris Maryasin ◽  
Leticia Gonzalez ◽  
...  
Keyword(s):  

2021 ◽  
Author(s):  
Miran Lemmerer ◽  
Margaux Riomet ◽  
Ricardo Meyrelles ◽  
Boris Maryasin ◽  
Leticia Gonzalez ◽  
...  
Keyword(s):  

Synlett ◽  
2021 ◽  
Author(s):  
Gustav J. Wørmer ◽  
Thomas Bjørnskov Poulsen

Piperidine alkaloids continue to challenge the synthetic community by featuring densely functionalized scaffolds which often requires careful chemical orchestration. Streptazone A and abikoviromycin are small and highly functionalized piperidine alkaloids both accommodating Michael acceptors and a labile epoxide. These moieties are loaded into a [4.3.0] bicyclic core also present in other structurally related natural products including the well-known piperidine alkaloid streptazolin. Herein, we cover ring-closing strategies employed in prior streptazolin syntheses, provide a concise overview of structures, biological properties and biosyntheses of selected [4.3.0] piperidine alkaloids, and finally we disclose a complete coverage of our recent asymmetric syntheses of streptazone A and abikoviromycin.


2021 ◽  
Vol 0 (0) ◽  
pp. 0-0
Author(s):  
Songuigama Coulibaly ◽  
Jean-Paul NGuessan Deto ◽  
Aboudramane Koné ◽  
Doumadé Zon ◽  
Mamidou Witabouna Koné ◽  
...  

2021 ◽  
Vol 17 ◽  
pp. 1689-1697
Author(s):  
Susanne M Fischer ◽  
Simon Renner ◽  
A Daniel Boese ◽  
Christian Slugovc

Electron-rich triarylphosphines, namely 4-(methoxyphenyl)diphenylphosphine (MMTPP) and tris(4-trimethoxyphenyl)phosphine (TMTPP), outperform commonly used triphenylphosphine (TPP) in catalyzing oxa-Michael additions. A matrix consisting of three differently strong Michael acceptors and four alcohols of varying acidity was used to assess the activity of the three catalysts. All test reactions were performed with 1 mol % catalyst loading, under solvent-free conditions and at room temperature. The results reveal a decisive superiority of TMTPP for converting poor and intermediate Michael acceptors such as acrylamide and acrylonitrile and for converting less acidic alcohols like isopropanol. With stronger Michael acceptors and more acidic alcohols, the impact of the more electron-rich catalysts is less pronounced. The experimental activity trend was rationalized by calculating the Michael acceptor affinities of all phosphine–Michael acceptor combinations. Besides this parameter, the acidity of the alcohol has a strong impact on the reaction speed. The oxidation stability of the phosphines was also evaluated and the most electron-rich TMTPP was found to be only slightly more sensitive to oxidation than TPP. Finally, the catalysts were employed in the oxa-Michael polymerization of 2-hydroxyethyl acrylate. With TMTPP polymers characterized by number average molar masses of about 1200 g/mol at room temperature are accessible. Polymerizations carried out at 80 °C resulted in macromolecules containing a considerable share of Rauhut–Currier-type repeat units and consequently lower molar masses were obtained.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tao-Tao Gao ◽  
Hou-Xiang Lu ◽  
Peng-Chao Gao ◽  
Bi-Jie Li

AbstractChiral tertiary boronic esters are important precursors to bioactive compounds and versatile synthetic intermediates to molecules containing quaternary stereocenters. The development of conjugate boryl addition to α,β-unsaturated amide has been hampered by the intrinsic low electrophilicity of the amide group. Here we show the catalytic asymmetric synthesis of enantioenriched tertiary boronic esters through hydroboration of β,β-disubstituted α,β-unsaturated amides. The Rh-catalyzed hydroboration occurs with previously unattainable selectivity to provide tertiary boronic esters in high enantioselectivity. This strategy opens a door for the hydroboration of inert Michael acceptors with high stereocontrol and may provide future applications in the synthesis of biologically active molecules.


Author(s):  
Brian R. Hearn ◽  
Shaun D. Fontaine ◽  
Eric L. Schneider ◽  
Yannick Kraemer ◽  
Gary W. Ashley ◽  
...  
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