N-Spiro Chiral Quaternary Ammonium Bromide Catalyzed Diastereo- and Enantioselective Conjugate Addition of Nitroalkanes to Cyclic α,β-Unsaturated Ketones under Phase-Transfer Conditions

2005 ◽  
Vol 7 (23) ◽  
pp. 5143-5146 ◽  
Author(s):  
Takashi Ooi ◽  
Saki Takada ◽  
Shingo Fujioka ◽  
Keiji Maruoka
Keyword(s):  
Quaternary Ammonium ◽  
Phase Transfer ◽  
Conjugate Addition ◽  
Ammonium Bromide ◽  
Unsaturated Ketones

scholarly journals A Remarkably Efficient Phase-Transfer Catalyzed Amination of α-Bromo-α, β-Unsaturated Ketones in Water

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Alemayehu Mekonnen ◽  
Alemu Tesfaye
Keyword(s):  
Quaternary Ammonium ◽  
Phase Transfer ◽  
Conjugate Addition ◽  
Quaternary Ammonium Salts ◽  
Cinchona Alkaloids ◽  
Ammonium Salts ◽  
Alkylation Reaction ◽  
Pt Catalysts ◽  
Unsaturated Ketones ◽  
Catalytic Performances

Tandem conjugate addition–alkylation reaction of various amines with α-bromo-α, β-unsaturated ketones resulted in near-quantitative conversions into the corresponding aziridines when the reaction was carried out in the presence of 10 mol% of phase-transfer, PT catalysts in water. Some chiral quaternary ammonium salts derived from Cinchona alkaloids were investigated as water-stable PT catalysts. The scope and limitations of the reaction have also been investigated. The catalytic performances were significantly improved in comparison with the corresponding ordinary quaternary ammonium salt catalysts, and excellent yields (81%–96%) were obtained. Although an increase in the rate of aziridination has been accomplished, no stereoselectivity was observed. The positive values of the protocol have been confirmed.

Ultrasonic assisted dimeric cinchona based chiral phase transfer catalysts for highly enanatioselective synthesis of epoxidation of α,β-unsaturated ketones

RSC Advances ◽  
2014 ◽  
Vol 4 (104) ◽  
pp. 60293-60299 ◽  
Author(s):  
Jayaraman Sivamani ◽  
Veeramanoharan Ashokkumar ◽  
Velu Sadhasivam ◽  
Kumaraguru Duraimurugan ◽  
Ayyanar Siva
Keyword(s):  
Ultrasonic Irradiation ◽  
Phase Transfer ◽  
Cinchona Alkaloids ◽  
Ammonium Bromide ◽  
Chiral Phase ◽  
Unsaturated Ketones ◽  
Phase Transfer Catalysts ◽  
Ultrasonic Assisted ◽  
Chiral Phase Transfer Catalysts ◽  
Enantioselective Epoxidation

New types of bis-quaternary ammonium bromide as chiral multisite phase transfer catalysts derived from cinchona alkaloids have been developed and evaluated for the enantioselective epoxidation of chalcones in the presence of lower concentrations of various oxidants, bases and ultrasonic irradiation conditions.

Ascorbate: antioxidant activity determined in a hydrocarbon phase using quaternary ammonium salts as phase-transfer agents

1992 ◽  
Vol 70 (8) ◽  
pp. 2148-2153 ◽  
Author(s):  
L. Ross C. Barclay ◽  
Kelly A. Dakin ◽  
Hayder A. Zahalka
Keyword(s):  
Antioxidant Activity ◽  
Quaternary Ammonium ◽  
Phase Transfer ◽  
Relative Effectiveness ◽  
Hydrogen Atom Transfer ◽  
Sodium Ascorbate ◽  
Ammonium Bromide ◽  
Phase System ◽  
Two Phase ◽  
Inhibition Rate Constant

By shaking sodium ascorbate with tetra-n-butyl ammonium bromide in a two-phase system consisting of water and organic phases, such as 1,1,2,2-tetrachloroethane (TCE) or chlorobenzene, sufficient concentrations of the quaternary ammonium-ascorbate (quat-ascorbate) are transferred into the organic phase to be useful for antioxidant studies in non-polar solvents. The antioxidant activity of the quat-ascorbate was determined by measurement of the (inhibition) rate constant, kinh, for the inhibition of autoxidation of styrene initiated thermally by azobisisobutyrylnitrile (AIBN) at 30 °C. The kinh of ascorbate in styrene, found to be (9.63 ± 2.0) × 104 M−1 s−1, is very much lower than that found for ascor-byl-6-palmitate, kinh = (110 ± 11) × 104 M−1 s−1 under these conditions. The differences are discussed in terms of the relative effectiveness of hydrogen-atom transfer from the enolic hydroxyl at position 2 of the ascorbate ion compared with the more facile such transfer from position 3 of ascorbyl 6-palmitate in a nonpolar medium.

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