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Scandium triflate-PYBOX complex

Fukuzawa et al. [99] found analogous scandium(III)triflate/ Pr-PyBOx complex as efficient catalyst for the asymmetric Diels-Alder reaction between cyclopentadiene or acyclic dienes and acyl-l,3-oxazohdin-2-ones with up to 90% ee. They latter described the same reaction in super critical CO2 in the presence of MSdA [ 100] that proceeded more rapidly than in CH2CI2 leading to the expected product with analogous selectivity. [Pg.123]

Allenyltrimethylsilanes add to ethyl glyoxalate in the presence of a chiral pybox scandium triflate catalyst to afford highly enantioenriched homopropargylic alcohols or dihydrofurans, depending on the nature of the silyl substituent (Tables 9.39 and 9.40) [62]. The trimethylsilyl-substituted silanes give rise to the alcohol products whereas the bulkier t-butyldiphenylsilyl (DPS)-substituted silanes yield only the [3 + 2] cycloadducts. A bidentate complex of the glyoxalate with the scandium metal center in which the aldehyde carbonyl adopts an axial orientation accounts for the observed facial preference ofboth additions. [Pg.538]

PYBOX complexes of scandium(III) triflate act as enantio- and diastereo-selective catalysts of ene reactions, including examples with trisubstituted alkenes.207... [Pg.23]

Enantiopure amide derivatives (64) of -unsaturated a-hydroxy acids have been made by addition of a vinylsilane, R2R1C=(4ISiMe3, to /V-phcnylglyoxamide.181 The reaction is catalysed by scandium(III) triflate complexed to a C2-symmetric PYBOX ligand derived from (f )-norephedrine. [Pg.24]

The asymmetric conjugate addition of thiophenol to ( >3-crotonoyloxazolidin-2-one, catalysed by the scandium(III) triflate complex of Ph-PYBOX, gave the corre- sponding adduct in 66% ee. Lanthanoid triflates gave lower enantioselectivities (<28% ee).132... [Pg.342]

Chiral 2-(3-oxoalkyl)pyrroles and 3-(3-oxoalkyl)indoles can also be accessed by reaction in the presence of 10 mol% of chiral bis(oxazoline)/metal complexes in CH2C12 in very high yields and with ee values over 90% <2005JA4154>. Alkylation of pyrrole and of substituted indoles with, -unsaturated acyl phosphonates <2003JA10780> or 2-acyl N-methylimidazoles catalyzed by a chiral bis(oxazolinyl)pyridine (pybox)/scandium(III) triflate complex also exhibits good enantioselectivity over a broad range of substrates <2005JA8942>. [Pg.409]

The Friedel-Crafts alkylation of the parent pyrrole and of substituted indoles with a,P-unsaturated acyl phospho-nates 468 <2003JA10780> and 2-acyl iV-methylimidazoles 469 catalyzed by the chiral bis(oxazolinyl)pyridine (pybox)/scandium(lIl) triflate complex 467 exhibits good enantioselectivities over a broad range of substrates (Scheme 97, Equation 113) <2005JA8942>. The desired alkylation products 470-472 were formed in good yields and enantioselectivities. [Pg.116]


See other pages where Scandium triflate-PYBOX complex is mentioned: [Pg.538]    [Pg.538]   
See also in sourсe #XX -- [ Pg.313 ]




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Scandium triflates

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