ChemInform Abstract: Hydride Reductions of 1H-Pyrrolo[2,1-c][1,4]benzodiazepine-5,11-diones: Selective Reduction of Secondary Amides to Carbinolamines.

ChemInform ◽  
2010 ◽  
Vol 30 (31) ◽  
pp. no-no
Author(s):  
Andrew G. Katsifis ◽  
Meredith E. McPhee ◽  
Damon D. Ridley
Keyword(s):  
Selective Reduction ◽  
Secondary Amides

Hydride Reductions of 1H-Pyrrolo[2,1-c][1,4]-benzodiazepine-5,11-diones: Selective Reduction of Secondary Amides to Carbinolamines

1998 ◽  
Vol 51 (12) ◽  
pp. 1121 ◽  
Author(s):  
Andrew G. Katsifis ◽  
Meredith E. McPhee ◽  
Damon D. Ridley
Keyword(s):  
Selective Reduction ◽  
Secondary Amide ◽  
Tertiary Amide ◽  
Secondary Amides

For the syntheses of radiolabelled pyrrolo[1,4]benzodiazepine antitumour antibiotics we required a method in which the unstable carbinolamine functionality was introduced prior to the radiolabel. In turn this required the selective reduction of a secondary amide in the presence of, inter alia, a tertiary amide. We report methods which can be used to achieve this outcome in a series of 1H-pyrrolo[2,1-c][1,4]benzodiazepine-5,11-diones.

Metal-Free Photoredox-Catalyzed C–H/C–H Coupling of Arenes Enabled by Interrupted Pummerer Activation

2019 ◽  
Author(s):  
Miles Aukland ◽  
Mindaugas Šiaučiulis ◽  
Adam West ◽  
Gregory Perry ◽  
David Procter
Keyword(s):  
Natural Product ◽  
Selective Reduction ◽  
Cross Coupling ◽  
One Pot ◽  
Complex Molecules ◽  
Pummerer Reaction ◽  
Metal Free ◽  
Bond Forming ◽  
Coupling Partner ◽  
Bioactive Natural Product

<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>

Diastereoselective Reduction of Selected α-substituted β-keto Esters and the Assignment of the Relative Configuration by 1H-NMR Spectroscopy

2020 ◽  
Vol 07 ◽  
Author(s):  
Christian Trapp ◽  
Corinna Schuster ◽  
Chris Drewniok ◽  
Dieter Greif ◽  
Martin Hofrichter
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
1H Nmr Spectroscopy ◽  
Selective Reduction ◽  
Reducing Agents ◽  
Relative Configuration ◽  
Curtius Rearrangement ◽  
Keto Esters ◽  
Hydroxy Esters ◽  
Diastereoselective Reduction

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.

Synthesis of 11-hydroxylated androstane derivatives

1980 ◽  
Vol 45 (6) ◽  
pp. 1845-1849 ◽  
Author(s):  
Jan Fajkoš ◽  
Jiří Joska
Keyword(s):  
Selective Reduction ◽  
Reaction Conditions ◽  
Androstane Derivatives

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

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