ChemInform Abstract: AMINOALUMINUM HYDRIDE AS NEW REDUCING AGENTS PART 1, SELECTIVE REDUCTION OF CARBOXYLIC ACIDS TO ALDEHYDES

1975 ◽  
Vol 6 (45) ◽  
pp. no-no
Author(s):  
M. MURAKI ◽  
T. MUKAIYAMA
Keyword(s):  
Carboxylic Acids ◽  
Selective Reduction ◽  
Reducing Agents

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.

Nickel-Catalyzed Selective Reduction of Carboxylic Acids to Aldehydes

2019 ◽  
Vol 21 (19) ◽  
pp. 7804-7808 ◽  
Author(s):  
Andrei V. Iosub ◽  
Štefan Moravčík ◽  
Carl-Johan Wallentin ◽  
Joakim Bergman
Keyword(s):  
Carboxylic Acids ◽  
Selective Reduction

ChemInform Abstract: Selective Reduction of Carboxylic Acids to Aldehydes Catalyzed by B(C6F5)3.

ChemInform ◽  
2013 ◽  
Vol 44 (24) ◽  
pp. no-no
Author(s):  
David Bezier ◽  
Sehoon Park ◽  
Maurice Brookhart
Keyword(s):  
Carboxylic Acids ◽  
Selective Reduction
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