Investigating the Ritter Type Reaction of α-Methylene-β-hydroxy Esters in Acidic Medium: Evidence for the Intermediacy of an Allylic Cation

2013 ◽  
Vol 2013 (23) ◽  
pp. 5180-5187 ◽  
Author(s):  
Marcus M. Sá ◽  
Misael Ferreira ◽  
Giovanni F. Caramori ◽  
Laize Zaramello ◽  
Adailton J. Bortoluzzi ◽  
...  
Keyword(s):  
Acidic Medium ◽  
Type Reaction ◽  
Allylic Cation ◽  
Hydroxy Esters

ChemInform Abstract: Synthesis of α-Fluoro-β-hydroxy Esters by an Enantioselective Reformatsky-Type Reaction.

ChemInform ◽  
2012 ◽  
Vol 43 (30) ◽  
pp. no-no
Author(s):  
Michal Fornalczyk ◽  
Kuldip Singh ◽  
Alison M. Stuart
Keyword(s):  
Type Reaction ◽  
Hydroxy Esters

Synthesis of α-fluoro-β-hydroxy esters by an enantioselective Reformatsky-type reaction

2012 ◽  
Vol 48 (29) ◽  
pp. 3500 ◽  
Author(s):  
Michal Fornalczyk ◽  
Kuldip Singh ◽  
Alison M. Stuart
Keyword(s):  
Type Reaction ◽  
Hydroxy Esters

Cerium-catalyzed reformatsky-type reaction with ethyl bromosuccinate for the synthesis of γ-lactones

Planta Medica ◽  
2012 ◽  
Vol 78 (11) ◽  
Author(s):  
S Muniz Machado Rodrigues ◽  
GVJ da Silva ◽  
M Gomes Constantino
Keyword(s):  
Type Reaction

Ag (I) Catalyzed Oxidation of SO2 in Aqueous Solution Differing Effect of Benzoate Ions in Acidic Medium

2017 ◽  
Vol 7 (4) ◽  
Author(s):  
Arun Kumar Sharma ◽  
Pradeep Parasher ◽  
Rashmi Sharma ◽  
Davarakonda S.N. Prasad
Keyword(s):  
Aqueous Solution ◽  
Acidic Medium ◽  
Differing Effect ◽  
Catalyzed Oxidation

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.

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