Zinc(II) Iodide-Directed β-Mannosylation: Reaction Selectivity, Mode, and Application

Author(s):  
Xuemei Zhong ◽  
Siai Zhou ◽  
Jiaming Ao ◽  
Aoxin Guo ◽  
Qian Xiao ◽  
...  
Keyword(s):  
2019 ◽  
Author(s):  
Łukasz Ciszewski ◽  
Jakub Durka ◽  
Dorota Gryko

This article describes direct photoalkylation of electron-rich aromatic compounds with diazo compoiunds. C-2 alkylated indoles and pyrroles are obtained with good yields even though the photocatalyst (Ru(bpy)3Cl2) loading is as low as 0.075 mol %. For substrates bearing electron-withdrawing substituents the addition of a catalytic amount of N,N-dimethyl-4-methoxyaniline is required. Both EWG-EWG and EWG-EDG substituted diazo esters are suitable as alkylating agents. The reaction selectivity and mechanistic experiments suggest that carbenes/carbenoid intermediates are not involved in the reaction pathway, instead radical formation is proposed.


2019 ◽  
Author(s):  
Elena Prigorchenko ◽  
Sandra Kaabel ◽  
Triin Narva ◽  
Anastassia Baškir ◽  
Maria Fomitšenko ◽  
...  

Amplification of a thermodynamically unfavoured macrocyclic product through the directed shift of the equilibrium between dynamic covalent chemistry library members is difficult to achieve. We show for the first time that during condensation of formaldehyde and <i>cis</i>-<i>N,N'</i>-cyclohexa-1,2-diylurea formation of <i>inverted-cis</i>-cyclohexanohemicucurbit[6]uril (<i>i-cis</i>-cycHC[6]) can be induced at the expense of thermodynamically favoured <i>cis</i>-cyclohexanohemicucurbit[6]uril (<i>cis</i>-cycHC[6]). The formation of <i>i-cis-</i>cycHC[6] is enhanced in low concentration of the templating chloride anion and suppressed in excess of this template. We found that reaction selectivity is governed by the solution-based template-aided dynamic combinatorial chemistry and continuous removal of the formed cycHC[6] macrocycles from the equilibrating solution by precipitation. Notably, the <i>i-cis</i>-cycHC[6] was isolated with 33% yield. Different binding affinities of three diastereomeric <i>i-cis</i>-, <i>cis</i>-cycHC[6] and their chiral isomer (<i>R,R</i>)-cycHC[6] for trifluoroacetic acid demonstrate the influence of macrocycle geometry on complex formation.


Author(s):  
Daria S. Timofeeva ◽  
David M Lindsay ◽  
W. J. Kerr ◽  
David James Nelson

Herein we examine the relationship between reaction rate and reaction selectivity in iridium-catalysed hydrogen isotope exchange (HIE) reactions directed by Lewis basic functional groups. We have recently develped a directing...


2021 ◽  
Vol 9 (10) ◽  
pp. 6252-6260
Author(s):  
Yi-Hsuan Wu ◽  
Denis A. Kuznetsov ◽  
Nicholas C. Pflug ◽  
Alexey Fedorov ◽  
Christoph R. Müller

Photoelectrodes based on bismuth vanadate demonstrate excellent performance in photoelectrochemical glycerol reforming.


Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 415
Author(s):  
Xinsheng Li ◽  
Jifeng Pang ◽  
Jingcai Zhang ◽  
Xianquan Li ◽  
Yu Jiang ◽  
...  

Catalytic conversion of biomass-derived feedstock to high-value chemicals is of remarkable significance for alleviating dependence on fossil energy resources. MgAl spinel-supported Pt catalysts were prepared and used in furfuryl alcohol conversion. The approaches to tune the reaction selectivity toward pentanediols (PeDs) were investigated and the catalytic performance was correlated to the catalysts’ physicochemical properties based on comprehensive characterizations. It was found that 1–8 wt% Pt was highly dispersed on the MgAl2O4 support as nanoparticles with small sizes of 1–3 nm. The reaction selectivity did not show dependence on the size of Pt nanoparticles. Introducing LiOH onto the support effectively steered the reaction products toward the PeDs at the expense of tetrahydrofurfuryl alcohol (THFA) selectivity. Meanwhile, the major product in PeDs was shifted from 1,5-PeD to 1,2-PeD. The reasons for the PeDs selectivity enhancement were attributed to the generation of a large number of medium-strong base sites on the Li-modified Pt catalyst. The reaction temperature is another effective factor to tune the reaction selectivity. At 230 °C, PeDs selectivity was enhanced to 77.4% with a 1,2-PeD to 1,5-PeD ratio of 3.7 over 4Pt/10Li/MgAl2O4. The Pt/Li/MgAl2O4 catalyst was robust to be reused five times without deactivation.


2021 ◽  
Author(s):  
Lei Zhang ◽  
Ruizhe Liu ◽  
Shiyang Lin ◽  
Jiangtao Xu

Reversible addition-fragmentation chain transfer (RAFT) single unit monomer insertion (SUMI) of β-Methylstyrene derivatives into diverse RAFT agents presented fast reaction kinetics, but a significant degradation of the SUMI products occurred...


2018 ◽  
Vol 58 (15) ◽  
pp. 6042-6048 ◽  
Author(s):  
Jeffrey A. Frumkin ◽  
Lorenz Fleitmann ◽  
Michael F. Doherty
Keyword(s):  

AIChE Journal ◽  
2017 ◽  
Vol 64 (3) ◽  
pp. 926-939 ◽  
Author(s):  
Jeffrey A. Frumkin ◽  
Michael F. Doherty

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