A new approach to remote asymmetric induction in the diastereoselective reduction of γ-keto esters by use of a chiral podand as chiral auxiliary

1991 ◽  
pp. 799-800 ◽  
Author(s):  
Yasufumi Tamai ◽  
Shinji Koike ◽  
Atsuhiko Ogura ◽  
Sotaro Miyano
Keyword(s):  
Chiral Auxiliary ◽  
Asymmetric Induction ◽  
New Approach ◽  
Keto Esters ◽  
Diastereoselective Reduction

ChemInform Abstract: Efficient 1,8- to 1,12-Asymmetric Induction in Grignard Reactions of ω-Keto Esters by Using BINOL or Its 2′-Oligoether Derivatives as the Chiral Auxiliary.

ChemInform ◽  
2010 ◽  
Vol 30 (39) ◽  
pp. no-no
Author(s):  
Yasufumi Tamai ◽  
Tetsutaro Hattori ◽  
Masamitsu Date ◽  
Hideki Takayama ◽  
Yoshinori Kamikubo ◽  
...  
Keyword(s):  
Chiral Auxiliary ◽  
Asymmetric Induction ◽  
Keto Esters ◽  
Grignard Reactions

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.

A New Approach to Fused 1,2-Diazepines by Cyclization of Enhydrazines with a- and b-Keto Esters

Heterocycles ◽  
1998 ◽  
Vol 47 (1) ◽  
pp. 315 ◽  
Author(s):  
Tetsuo Yamasaki ◽  
Kaoru Nishida ◽  
Yoshinari Okamoto ◽  
Tadashi Okawara ◽  
Mitsuru Furukawa
Keyword(s):  
New Approach ◽  
Keto Esters

Photochemistry of 9-methylbicyclo[3.3.1]nonyl aryl ketones — A novel 1,5-disproportionation of 1,4-hydroxy biradicals and asymmetric induction using the solid-state ionic chiral auxiliary method

2005 ◽  
Vol 83 (9) ◽  
pp. 1460-1472 ◽  
Author(s):  
Shuang Chen ◽  
Brian O Patrick ◽  
John R Scheffer
Keyword(s):  
Solid State ◽  
Single Crystal ◽  
Solid State Ionic ◽  
Chiral Auxiliary ◽  
Asymmetric Induction ◽  
X Ray Crystallography ◽  
Aryl Ketones ◽  
Hydroxy Biradicals ◽  
Phenyl Ketones ◽  
State Ionic

A novel 1,5-disproportionation reaction has been discovered for 1,4-hydroxy biradicals derived from the photolysis of 9-methylbicyclo[3.3.1]nonyl phenyl ketones (1), which undergo mainly Yang cyclization both in solution and the solid state. By applying the solid-state ionic chiral auxiliary method of asymmetric synthesis to the Yang cyclization, enantiomeric excesses as high as 95% were achieved at high reaction conversions. The origin of the reaction selectivity is discussed with the help of X-ray crystallography. In addition, the solid-state photoreaction of ketone 1b was found to occur in a single crystal-to-single crystal fashion.Key words: photochemistry, 1,4-hydroxy biradical, disproportionation, asymmetric induction, ionic chiral auxiliary, single crystal-to-single crystal reaction.

scholarly journals Asymmetric Electrophilic Difluoromethylthiolation of Indanone-Based β-Keto Esters Using Difluoromethanesulfonyl Hypervalent Iodonium Ylides

Molecules ◽  
2019 ◽  
Vol 24 (2) ◽  
pp. 221 ◽  
Author(s):  
Satoshi Gondo ◽  
Okiya Matsubara ◽  
Hélène Chachignon ◽  
Yuji Sumii ◽  
Dominique Cahard ◽  
...  
Keyword(s):  
Chiral Auxiliary ◽  
Direct Introduction ◽  
Keto Esters ◽  
Iodonium Ylides

The first electrophilic diastereoselective direct introduction of the difluoromethylthio group is described. We used a chiral auxiliary-based approach to illustrate the versatility of our recently developed difluoromethanesulfonyl hypervalent iodonium ylide reagents for the difluoromethylthiolation of indanone-based β-keto esters. Chiral SCF2H-featuring compounds were obtained in up to 93% ee value.

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