Asymmetric Calcium Catalysis: Highly Enantioselective Carbonyl-Ene and Friedel-Crafts Reactions for the Synthesis of Quaternary α-Hydroxy Esters Bearing a Trifluoromethyl Group

2012 ◽  
Vol 7 (6) ◽  
pp. 1195-1198 ◽  
Author(s):  
Magnus Rueping ◽  
Teerawut Bootwicha ◽  
Supakeat Kambutong ◽  
Erli Sugiono
Keyword(s):  
Trifluoromethyl Group ◽  
Hydroxy Esters ◽  
Calcium Catalysis

Highly diastereo- and enantioselective organocatalytic synthesis of trifluoromethylated erythritols based on the in situ generation of unstable trifluoroacetaldehyde

2021 ◽  
Author(s):  
Kazumasa Funabiki ◽  
Toshiya Gotoh ◽  
Ryunosuke Kani ◽  
Toshiyasu Inuzuka ◽  
Yasuhiro Kubota
Keyword(s):  
Trifluoromethyl Group ◽  
In Situ Generation

A highly diastereo- and enantioselective organocatalytic method to synthesise erythritols bearing a trifluoromethyl group has been investigated.

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.

Bu4N+-Controlled Addition and Olefination with Ethyl 2-(Trimethylsilyl)acetate via Silicon Activation

Synlett ◽  
2017 ◽  
Vol 28 (18) ◽  
pp. 2401-2406 ◽  
Author(s):  
Donal O’Shea ◽  
Manas Das ◽  
Atul Manvar ◽  
Ian Fox ◽  
Dilwyn Roberts
Keyword(s):  
Room Temperature ◽  
Product Formation ◽  
Unsaturated Ester ◽  
Reaction Conditions ◽  
Diverse Range ◽  
Inorganic Cation ◽  
Tetrabutyl Ammonium ◽  
Aldehydes And Ketones ◽  
Subsequent Elimination ◽  
Hydroxy Esters

Catalytic Bu4NOAc as silicon activator of ethyl 2-(trimethylsilyl)acetate, in THF, was utilized for the synthesis of β-hydroxy esters, whereas employing catalytic Bu4NOTMS gave α,β-unsaturated esters. The established reaction conditions were applicable to a diverse range of aromatic, heteroaromatic, aliphatic aldehydes and ketones. Reactions were achieved at room temperature without taking any of the specialized precautions that are in place for other organometallics. A stepwise olefination pathway via silylated β-hydroxy esters with subsequent elimination to form the α,β-unsaturated ester has been demonstrated. The key to selective product formation lies in use of the weaker acetate activator which suppresses subsequent elimination whereas stronger TMSO– activator (and base) facilitates both addition and elimination steps. The use of tetrabutyl ammonium salts for both acetate and trimethylsilyloxide activators provide enhanced silicon activation when compared to their inorganic cation counterparts.

Reducibility of the carbon-fluorine bond in the trifluoromethyl group

1996 ◽  
Vol 407 (1-2) ◽  
pp. 195-202 ◽  
Author(s):  
C. Combellas ◽  
F. Kanoufi ◽  
A. Thiébault
Keyword(s):  
Trifluoromethyl Group

Polyimide Copolymers Containing Various Levels Of The 6F Moiety For High Temperature And Microelectronic Applications

1991 ◽  
Vol 227 ◽  
Author(s):  
M. Haider ◽  
E. Chenevey ◽  
R. H. Vora ◽  
W. Cooper ◽  
M. Glick ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Electrical Properties ◽  
Oxidative Stability ◽  
Trifluoromethyl Group ◽  
Thermal And Mechanical Properties

ABSTRACTTrifluoromethyl group-containing polyimides not only show extraordinary electrical properties, but they also exhibit excellent long-term thermo-oxidative stability. Among the most thermomechanically stable structural polyimides are those from 6F dianhydride (6FDA) and 6F diamines. The effects of substituting non-fluorine containing monomers such as BTDA, mPDA and 4,4′-DADPS for the hexafluoroisopropylidene monomers on the dielectric, thermo-oxidative, thermal and mechanical properties of the copolymers were studied.

ChemInform Abstract: Synthesis of Imidazo(4,5-c)pyridines with a Trifluoromethyl Group at C- 4 and/or C-6.

ChemInform ◽  
2010 ◽  
Vol 26 (12) ◽  
pp. no-no
Author(s):  
R. K. GAUTAM ◽  
S. FUJII ◽  
M. NISHIDA ◽  
H. KIMOTO ◽  
L. A. COHEN
Keyword(s):  
Trifluoromethyl Group
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