Activation of reducing agents. Sodium hydride-containing complex reducing agents. 15. Reduction and selective reduction of organic halides

1981 ◽  
Vol 46 (7) ◽  
pp. 1270-1277 ◽  
Author(s):  
Regis Vanderesse ◽  
Jean Jacques Brunet ◽  
Paul Caubere
Keyword(s):  
Selective Reduction ◽  
Sodium Hydride ◽  
Reducing Agents ◽  
Organic Halides

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.

The Tetrakis(trimethylphosphine)cobalt Anion

1977 ◽  
Vol 32 (2) ◽  
pp. 138-143 ◽  
Author(s):  
Reinhard Hammer ◽  
Hans-Friedrich Klein
Keyword(s):  
Solid State ◽  
Alkali Metals ◽  
Reducing Agents ◽  
Phosphine Ligands ◽  
Organic Halides ◽  
Oxidative Additions ◽  
Reversible Formation ◽  
Inorganic And Organic

Reduction of paramagnetic L4Co (L = (CH3)3P) (d9) by alkali metals affords salts of L4Co- (d10). These are strong reducing agents, powerful bases and very able nucleophiles. They rapidly exchange three of their phosphine ligands for CO. Their reactions with a variety of inorganic and organic halides are shown to be effectively oxidative additions. From the distinct thermochromic behaviour of these salts both in the solid state and in solution a reversible formation involving different states of solvation is deduced.

ChemInform Abstract: One-Pot Etherification of Ketones and Aldehydes with Organic Halides Using Sodium Hydride as a Reductant

ChemInform ◽  
2009 ◽  
Vol 40 (42) ◽  
Author(s):  
Qingwei Meng ◽  
Bin Gong ◽  
Chuang Hui ◽  
Zhanxian Gao
Keyword(s):  
Sodium Hydride ◽  
One Pot ◽  
Organic Halides
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