184046-33-1Relevant academic research and scientific papers
Asymmetric Epoxidation of Unfunctionalized Olefins Using Novel Chiral Dihydroisoquinolinium Salts as Organocatalysts
Ali, K. Ben
, p. 638 - 646 (2021/06/02)
Abstract: Two new non-racemic chiral dihydroisoquinolinium salts with N-substituents bulkier than a methyl group have been synthesized from (1S,2R)-norephedrine. These salts were used to catalyze asymmetric epoxidation of a series of prochiral olefins. One of the two new catalysts provided higher enantioselectivities (up to 66% ee) than the reference salt containing an N-methyl substituent.
Preparation of C 2-Symmetric Biaryl Bisiminium Salts and Their Use as Organocatalysts for Asymmetric Epoxidation
Bulman Page, Philip C.,Farah, Mohamed M.,Buckley, Benjamin R.,Chan, Yohan,Blacker, A. John
, p. 126 - 130 (2015/12/26)
Two C 2-symmetric bisiminium salt species containing biphenylazepinium units and derived from two chiral diamines were prepared and tested as organocatalysts for asymmetric epoxidation.
New biphenyl iminium salt catalysts for highly enantioselective asymmetric epoxidation: Role of additional substitution and dihedral angle
Bulman Page, Philip C.,Bartlett, Christopher J.,Chan, Yohan,Allin, Steven M.,McKenzie, Michael J.,Lacour, Jér?me,Jones, Garth A.
, p. 4220 - 4232 (2016/05/24)
New biaryl iminium salt catalysts for enantioselective alkene epoxidation containing additional substitution in the heterocyclic ring are reported. The effects upon conformation and enantioselectivity of this additional substitution, and the influence of dihedral angle in these systems, has been investigated using a synthetic approach supported by density functional theory. Enantioselectivities of up to 97% ee were observed.
Carbohydrate-derived iminium salt organocatalysts for the asymmetric epoxidation of alkenes
Bulman Page, Philip C.,Chan, Yohan,Liddle, John,Elsegood, Mark R.J.
, p. 7283 - 7305 (2017/09/13)
A new family of carbohydrate-based dihydroisoquinolinium salts has been prepared and tested for potential as asymmetric catalysts for the epoxidation of unfunctionalized alkene substrates, providing up to 57% ee in the product epoxides.
Asymmetric epoxidation using iminium salt organocatalysts featuring dynamically controlled atropoisomerism
Bulman Page, Philip C.,Bartlett, Christopher J.,Chan, Yohan,Day, David,Parker, Phillip,Buckley, Benjamin R.,Rassias, Geracimos A.,Slawin, Alexandra M. Z.,Allin, Steven M.,Lacour, Jerome,Pinto, Andre
experimental part, p. 6128 - 6138 (2012/10/08)
Introduction of a pseudoaxial substituent at a stereogenic center adjacent to the nitrogen atom in binaphthyl- and biphenyl-derived azepinium salt organocatalysts affords improved enantioselectivities and yields in the epoxidation of unfunctionalized alkenes. In the biphenyl-derived catalysts, the atropoisomerism at the biphenyl axis is controlled by the interaction of this substituent with the chiral substituent at nitrogen.
L-proline-derived dendritic tetrakis(diperoxotungsto)phosphate: Synthesis and enantioselective oxidation catalysis
Jahier, Claire,Nlate, Sylvain
experimental part, p. 833 - 840 (2012/03/11)
As a part of our ongoing research towards the synthesis of chiral dendritic polyoxometalate (DENDRI-POM) hybrids that are able to catalyze oxidation of organic substrates with high selectivity and enantioselectivity, we have prepared an enantiopure DENDRI-POM salt by coupling a well-defined L-proline-derived tetrapropylammonium dendron with the tetrakis(diperoxotungsto) phosphate [PO4{WO(O2)2}4] 3-. This DENDRI-POM hybrid was characterized by infrared, NMR spectroscopy, polarimetry, and elemental analysis. The data obtained are consistent with the structure in which the trianionic POM is surrounded by three L-proline-based dendrons. This DENDRI-POM oxidized sulfides with moderate activity and very low enantioselectivities (up to 4 %), whereas alkenes were efficiently oxidized with up to 37 % enantiomeric excess (ee), and good yields. Although these ee values are still not satisfactory for practical asymmetric synthesis, 37 % ee represents the best enantioselectivity reported to date in the oxidation of organic substrate with chiral POM hybrids. Studies of temperature, solvent, and catalyst loading effects on the outcome of the reaction indicate that the ee is sensitive to the nature of the solvent. Moreover, the catalyst was recovered at low temperature and reused while retaining its activity and enantioselectivity. These results contrast and complement our reported results in which DENDRI-POMs based on phenylethylamine-derived ligands efficiently oxidize sulfides with up to 14 % ee, whereas alkenes were not oxidized with this family of chiral POM compounds. Thus, the influence of the nature of the chiral countercation on the POM properties is again observed. L-Proline-derived dendritic tetrakis(diperoxotungsto)phosphate was prepared byassembling enantiopure L-proline-derived ligands with the anionic polyoxometalate (POM) unit. This DENDRI-POM catalyzes the oxidation of alkenes to the corresponding epoxides with 37 % ee. This ee value is the best enantioselectivity reported to date in the oxidation of organic substrates with chiral POM hybrids. Copyright
Synthesis of new carbohydrate-derived ketones as organocatalysts in the enantioselective epoxidation of arylalkenes. Part 2: Chiral ketones from sugars
Vega-Pérez, José M.,Vega-Holm, Margarita,Peri?án, Ignacio,Palo-Nieto, Carlos,Iglesias-Guerra, Fernando
experimental part, p. 364 - 372 (2011/03/20)
A range of new, somewhat complex, stereochemically varied, and structurally related carbohydrate-derived ketones were synthesised by a simple method from the carbohydrate precursor (d-gluco and d-galacto derivatives). The common skeleton possesses the keto function sited on a seven-membered ring fused to positions 2 and 3 of the sugar moiety. Their chirality transfer capability in the dioxirane-mediated epoxidation of arylalkenes was evaluated. Copyright
Iron-catalyzed asymmetric epoxidation of β,β-disubstituted enones
Nishikawa, Yasuhiro,Yamamoto, Hisashi
supporting information; experimental part, p. 8432 - 8435 (2011/07/29)
The combination of Fe(OTf)2 and novel phenanthroline ligands enables the catalytic asymmetric epoxidation of acyclic β,β- disubstituted enones, which have been a heretofore inaccessible substrate class. The reaction provides highly enantioenriched α,β-epoxyketones (up to 92% ee) that can be further converted to functionalized β-ketoaldehydes with an all-carbon quaternary center.
New mannose-derived ketones as organocatalysts for enantioselective dioxirane-mediated epoxidation of arylalkenes. Part 3: Chiral ketones from sugars
Vega-Pérez, José M.,Peri?án, Ignacio,Vega-Holm, Margarita,Palo-Nieto, Carlos,Iglesias-Guerra, Fernando
experimental part, p. 7057 - 7065 (2011/10/05)
New d-arabino-hexopyranosid-3-uloses were synthesized by a simple method from mannopyranoside derivatives. The common skeleton possesses a tunable alkoxy group as steric sensor on carbon 2 of the sugar. The new ketones were employed in the dioxirane-mediated epoxidation of a range of trans- and trisubstituted arylalkenes giving enantiomeric excesses from low to good (30-90%). The effect of the size of the steric sensor on the enantioselectivity was also studied. The least bulky group (methoxy group) enhanced the stereoselectivity (up to 90% ee toward triphenylethylene).
Catalytic asymmetric epoxidation of alkenes with arabinose-derived ketones containing a cyclohexane-1,2-diacetal
Shing, Tony K.M.,Luk, To
experimental part, p. 883 - 886 (2009/09/08)
The effect of diol blocking groups, cyclohexane-1,2-diacetal verses butane-1,2-diacetal, on the asymmetric epoxidation of trans- and cis-alkenes by arabinose-derived ketones is reported. The ketone catalysts with a cyclohexane-1,2-acetal display similar asymmetric induction as those catalysts with a butane-1,2-diacetal in most cases. For (E)-1-benzyloxy-4-hexene, the ee of the enantioselective epoxidation has reached 61% with the cyclohexane-1,2-dineopentyl acetal ketone catalyst.
