Tandem Chain Extension-Homoenolate Formation:  The Formation of α-Methylated-γ-Keto Esters

2001 ◽  
Vol 3 (19) ◽  
pp. 3037-3040 ◽  
Author(s):  
Ramona Hilgenkamp ◽  
Charles K. Zercher
Keyword(s):  
Chain Extension ◽  
Keto Esters

Formation of β-Substituted γ-Keto Esters via Zinc Carbenoid Mediated Chain Extension

Synthesis ◽  
2007 ◽  
Vol 2007 (15) ◽  
pp. 2404-2408 ◽  
Author(s):  
Charles Zercher ◽  
Weimin Lin ◽  
Robert McGinness ◽  
Emerald Wilson
Keyword(s):  
Chain Extension ◽  
Keto Esters ◽  
Zinc Carbenoid

scholarly journals A Combined DFT and NMR Investigation of the Zinc Organometallic Intermediate Proposed in theSyn-Selective Tandem Chain Extension–Aldol Reaction of β-Keto Esters

2012 ◽  
Vol 77 (14) ◽  
pp. 5942-5955 ◽  
Author(s):  
Karelle S. Aiken ◽  
Wilhelm A. Eger ◽  
Craig M. Williams ◽  
Carley M. Spencer ◽  
Charles K. Zercher
Keyword(s):  
Aldol Reaction ◽  
Chain Extension ◽  
Keto Esters

Zinc-Mediated Ring-Expansion and Chain-Extension Reactions of β-Keto Esters

2005 ◽  
Vol 70 (20) ◽  
pp. 8245-8247 ◽  
Author(s):  
Song Xue ◽  
Yong-Kang Liu ◽  
Le-Zhen Li ◽  
Qing-Xiang Guo
Keyword(s):  
Ring Expansion ◽  
Chain Extension ◽  
Keto Esters

scholarly journals Zinc-Mediated Ring-Expansion and Chain-Extension Reactions of β-Keto Esters.

ChemInform ◽  
2006 ◽  
Vol 37 (4) ◽  
Author(s):  
Song Xue ◽  
Yong-Kang Liu ◽  
Le-Zhen Li ◽  
Qing-Xiang Guo
Keyword(s):  
Ring Expansion ◽  
Chain Extension ◽  
Keto Esters

Formation of β-Substituted γ-Keto Esters via Zinc Carbenoid Mediated Chain Extension.

ChemInform ◽  
2007 ◽  
Vol 38 (48) ◽  
Author(s):  
Weimin Lin ◽  
Robert J. McGinness ◽  
Emerald C. Wilson ◽  
Charles K. Zercher
Keyword(s):  
Chain Extension ◽  
Keto Esters ◽  
Zinc Carbenoid

Towards Enantioselective Electrophilic Trifluoromethylation of β-Keto Esters

2006 ◽  
Author(s):  
Dominique Cahard ◽  
Jun-An Ma ◽  
Vitaliy Petrik
Keyword(s):  
Keto Esters

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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