Surface Synergetic Effects of Pt clusters/monolayer Bi2MoO6 Nanosheet for Promoting the Photocatalytic Selective Reduction of 4-nitrostyrene to 4-vinylaniline

Author(s):  
Yingzhang Shi ◽  
Zhiwen Wang ◽  
Cheng Liu ◽  
Tai kang Wu ◽  
Rui Liu ◽  
...  
2019 ◽  
Author(s):  
Miles Aukland ◽  
Mindaugas Šiaučiulis ◽  
Adam West ◽  
Gregory Perry ◽  
David Procter

<p>Aryl–aryl cross-coupling constitutes one of the most widely used procedures for the synthesis of high-value materials, ranging from pharmaceuticals to organic electronics and conducting polymers. The assembly of (hetero)biaryl scaffolds generally requires multiple steps; coupling partners must be functionalized before the key bond-forming event is considered. Thus, the development of selective C–H arylation processes in arenes, that side-step the need for prefunctionalized partners, is crucial for streamlining the construction of these key architectures. Here we report an expedient, one-pot assembly of (hetero)biaryl motifs using photocatalysis and two non-prefunctionalized arene partners. The approach is underpinned by the activation of a C–H bond in an arene coupling partner using the interrupted Pummerer reaction. A unique pairing of the organic photoredox catalyst and the intermediate dibenzothiophenium salts enables highly selective reduction in the presence of sensitive functionalities. The utility of the metal-free, one-pot strategy is exemplified by the synthesis of a bioactive natural product and the modification of complex molecules of societal importance.</p>


2020 ◽  
Vol 07 ◽  
Author(s):  
Christian Trapp ◽  
Corinna Schuster ◽  
Chris Drewniok ◽  
Dieter Greif ◽  
Martin Hofrichter

Background:: Chiral β-hydroxy esters and α-substituted β-hydroxy esters represent versatile building blocks for pheromones, β-lactam antibiotics and 1,2- or 1,3-aminoalcohols. Objective:: Synthesis of versatile α-substituted β-keto esters and their diastereoselective reduction to the corresponding syn- or anti-α-substituted β-hydroxy esters. Assignment of the relative configuration by NMR-spectroscopy after a CURTIUS rearrangement of α-substituted β-keto esters to 4-substituted 5-methyloxazolidin-2-ones. Method:: Diastereoselective reduction was achieved by using different LEWIS acids (zinc, titanium and cerium) in combination with complex borohydrides as reducing agents. Assignment of the relative configuration was verified by 1H-NMR spectroscopy after CURTIUS-rearrangement of α-substituted β-hydroxy esters to 4-substituted 5-methyloxazolidin-2-ones. Results:: For the syn-selective reduction, titanium tetrachloride (TiCl4) in combination with a pyridine-borane complex (py BH3) led to diastereoselectivities up to 99% dr. High anti-selective reduction was achieved by using cerium trichloride (CeCl3) and steric hindered reducing agents such as lithium triethylborohydride (LiEt3BH). After CURTIUS-rearrangement of each α-substituted β-hydroxy ester to the corresponding 4-substituted 5-methyloxazolidin-2-one, the relative configuration was confirmed by 1H NMR-spectroscopy. Conclusion:: We have expanded the procedure of LEWIS acid-mediated diastereoselective reduction to bulky α-substituents such as the isopropyl group and the electron withdrawing phenyl ring.


1980 ◽  
Vol 45 (6) ◽  
pp. 1845-1849 ◽  
Author(s):  
Jan Fajkoš ◽  
Jiří Joska

Reaction conditions for selective reduction of 3- and 17-oxo groups are described and applied to syntheses of 11-hydroxylated derivatives.


1992 ◽  
Vol 57 (7) ◽  
pp. 1483-1486 ◽  
Author(s):  
Václav Kozmík ◽  
Jaroslav Paleček

Selective reduction of a mixture of methyl 4-chloromethyl-2-thiophenecarboxylate (I) and the 5-chloromethyl isomer II, prepared by chloromethylation of methyl 2-thiophenecarboxylate (III), gave pure 4-chloromethyl derivative I and 5-methyl-2-thiophenecarboxylate (V) which on treatment with sulfuryl chloride was converted into the 5-chloromethyl isomer II.


2020 ◽  
Vol 37 ◽  
pp. 100990
Author(s):  
Brandon L. Panaro ◽  
Bernardo Yusta ◽  
Dianne Matthews ◽  
Jacqueline A. Koehler ◽  
Youngmi Song ◽  
...  
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