Asymmetric catalytic cyclopropanation of olefins: bis-oxazoline copper complexes

Lowenthal, Richard; Abiko, Atsushi; Masamune, Satoru

doi:10.1016/s0040-4039(00)98014-6

Cited by 521 publications

(122 citation statements)

References 18 publications

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“…These results are comparable to the results with the most efficient catalysts reported to date, including Cu-semicorrin, Cu-bisoxazoline, Cu-bipyridine, etc. [10][11][12][13][14][15][16][17][18][19] Furthermore, when one or two chlorine atoms or nitro groups are introduced, the ligands formed are easy to purify due to their high melting points. A recrystallization is sufficient to purify them.…”

Section: Resultsmentioning

confidence: 99%

Asymmetric Cyclopropanation of Styrene Catalyzed by Cu–(Chiral Schiff-Base) Complexes

Liu

Zheng

et al. 2000

Tetrahedron

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Section: Resultsmentioning

confidence: 99%

Asymmetric Cyclopropanation of Styrene Catalyzed by Cu–(Chiral Schiff-Base) Complexes

Liu

Zheng

et al. 2000

Tetrahedron

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“…In the presence of chiral bisoxazoline copper catalysts, 2-trimethylsilyloxybutadiene is reacted with methyl diazoacetate to give the cis-derivative with A 95% enantiomeric excess 51) . Furthermore, it is known from many examples in literature that bulky ester groups in the diazo component can strongly increase the selectivity of the cyclopropanation 52,53) . In contrast to other methods, carbene addition allows the introduction of several reactive substituents (e. g. halogen), which is fundamental for further derivatizations.…”

Section: Synthesis Of Vinylcyclopropanesmentioning

confidence: 99%

Synthesis and polymerization of vinylcyclopropanes

Moszner

Zeuner

Völkel

et al. 1999

Macromol. Chem. Phys.

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SUMMARY: Vinylcyclopropanes are important synthetic intermediates in organic chemistry and are mostly synthesized by the simultaneous introduction of the cyclopropane and the vinyl unit, e. g., by the reaction of trans-1,4-dihalobutenes with b -dicarbonyl compounds or the addition of carbenes to dienes. The polymerization of vinylcyclopropane itself results in vinyl polymers with predominantly 1,2-structural units. The radical polymerization of substituted vinylcyclopropanes results in polymers with mainly 1,5-ring-opened units, whereby radical stabilizing substituents or electron-withdrawing groups increase the radical polymerizability and the ring-opening ability. The vinylcyclopropanes undergo a radical copolymerization with other vinyl monomers, such as methacrylates, and, in comparison to the polymerization of these linear vinyl monomers, the vinylcyclopropanes show a significantly lower volume shrinkage during ring-opening polymerization. Hybrid vinylcyclopropanes are polymerized step-by-step under formation of reactive polymers or polymer networks. Multifunctional cross-linking vinylcyclopropanes can be used as new low-shrinking matrix monomers for photopolymerizable materials. In addition, the sol-gel process of trialkoxysilyl-functionalized vinylcyclopropanes affords low shrinking organic-inorganic nanocomposites.

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“…[6] Various chiral ligands have been described for the enantioselective versions of the cyclopropanation reaction, including salicylaldimines, [7] salicylaldehyde±amino acid derivatives, [8] and semicorrins. [9] The best results have been obtained with bis(oxazolines)-described independently by Evans and co-workers [10] and Masamune and co-workers [11] -which can lead to almost complete enantioselectivity (up to 99 % ee) when their complexes with Cu I or Cu II are used in cyclopropanation reactions. Good performance of chiral bis(oxazolines) as ligands for asymmetric cyclopropanation, as well as for other Lewis acid catalyzed reactions, has resulted in the recent commercial availability of some of them.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Insights into the Role of a Counterion in Copper‐Catalyzed Enantioselective Cyclopropanation Reactions

Fraile

Garcı́a

Gil

et al. 2004

Chemistry A European J

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The effect of a coordinating counteranion on the mechanism of Cu(I)-catalyzed cyclopropanation has been investigated extensively for a medium-sized reaction model by means of theoretical calculations at the B3LYP/6-31G(d) level. The main mechanistic features are similar to those found for the cationic (without a counteranion) mechanism, the rate-limiting step being nitrogen extrusion from a catalyst-diazoester complex to generate a copper-carbene intermediate. The cyclopropanation step takes place through a direct carbene insertion of the metal-carbene species to yield a catalyst-product complex, which can finally regenerate the starting complex. However, the presence of the counteranion has a noticeable influence on the calculated geometries of all the intermediates and transition structures. Furthermore, the existence of a preequilibrium with a dimeric form of the catalyst, together with a higher activation barrier in the insertion step, explains the lower yield of cyclopropane products observed experimentally in the presence of chloride counterion. The stereochemical predictions of a more realistic model (made by considering a chiral bis(oxazoline)-copper(i) catalyst) have been rationalized in terms of the lack of significant steric repulsions, and the model shows good agreement with the low enantioselectivities observed experimentally for these kinds of catalytic systems.

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Asymmetric catalytic cyclopropanation of olefins: bis-oxazoline copper complexes

Cited by 521 publications

References 18 publications

Asymmetric Cyclopropanation of Styrene Catalyzed by Cu–(Chiral Schiff-Base) Complexes

Asymmetric Cyclopropanation of Styrene Catalyzed by Cu–(Chiral Schiff-Base) Complexes

Synthesis and polymerization of vinylcyclopropanes

Theoretical Insights into the Role of a Counterion in Copper‐Catalyzed Enantioselective Cyclopropanation Reactions

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