Asymmetric ene reaction catalyzed by chiral organoaluminum reagent

Maruoka, Keiji; Hoshino, Yorihisa; Shirasaka, Tadashi; Yamamoto, Hisashi

doi:10.1016/s0040-4039(00)80395-0

Cited by 157 publications

(64 citation statements)

References 16 publications

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“…Chemical shifts are reported in ppm relative to an internal standard: tetramethylsilane (0 ppm) for 1 H NMR and deuteriocholorform (77.0 ppm) for 13 C NMR spectra. EI (70 ev) and ESI mass spectra were obtained by using HP5989 A and Mariner LC-TOF spectrometers, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…[12] Among various chiral Lewis acids, such as Al, Ti, Ni, Pt, Pd, Yb, and Cu metallic complexes, titanium complexes of BINOL derivatives are among the most widely used for asymmetric carbonyl-ene reactions. [12][13][14] According to Mikamis asymmetric activation concept, an enantiopure [(R)-BINOL-Ti(OiPr) 2 ] (10 mol %) catalyst could be activated by the further addition of (R)-BINOL(H 2 ), affording the product of the carbonyl-ene reaction in higher enantioselectivity (96.8 % ee vs 94.5 % ee). [14] Results of a kinetic study showed that the reaction catalyzed by the [(R)-BINOL-Ti-(OiPr) 2 -(R)-BINOL(H 2 )] complex was 25.6 times faster than that catalyzed by [(R)-BINOL-Ti(OiPr) 2 ].…”

Section: Synthesis Of Multitopic Binol Ligandsmentioning

confidence: 99%

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Self‐Supported Heterogeneous Titanium Catalysts for Enantioselective Carbonyl–Ene and Sulfoxidation Reactions

Wang

Guo

et al. 2005

Chemistry A European J

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A new strategy for the heterogenization of chiral titanium complexes was developed by the in situ assembly of bridged multitopic BINOL ligands with [Ti(OiPr)4] without using a support. The assembled heterogeneous catalysts (self-supported) showed excellent enantioselectivity in both the carbonyl-ene reaction of alpha-methylstyrene with ethyl glyoxylate (up to 98 % ee) and the oxidation of sulfides (up to >99 % ee). The catalytic performance of these heterogeneous catalytic systems was comparable or even superior to that attained with their homogeneous counterparts. The spacers between the two BINOL units of the ligands in the assembled catalysts had significant impact on the enantioselectivity of the carbonyl-ene reaction. This demonstrates the importance of the supramolecular structures of the assemblies on their catalytic behavior. In the catalysis of sulfoxidation, the self-supported heterogeneous titanium catalysts were highly stable and could be readily recycled and reused for over one month (at least eight cycles) without significant loss of activity and enantioselectivity (up to >99.9 % ee). The features of these self-supported catalysts, such as facile preparation, robust chiral structure of solid-state catalysts, high density of the catalytically active units in the solids, as well as easy recovery and simple recycling, are particularly important in developing methods for the synthesis of optically active compounds in industrial processes.

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Section: Methodsmentioning

confidence: 99%

Section: Synthesis Of Multitopic Binol Ligandsmentioning

confidence: 99%

Self‐Supported Heterogeneous Titanium Catalysts for Enantioselective Carbonyl–Ene and Sulfoxidation Reactions

Wang

Guo

et al. 2005

Chemistry A European J

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“…The thermal pericyclic ene reaction represents a typical concerted pathway involving six electrons with a suprafacial orbital interaction, [5] and its asymmetric version has been achieved with various chiral Lewis acids including Al, Ti, Ni, Pt, Pd, Yb, and Cu complexes. [6,7] The catalyst loadings employed in most cases were in the range from 1 to 10 mol %. In our experiments we employed binolate-Ti, which was prepared in situ by the reaction of (R)-binol (2,2'-dihydroxy-1,1'-biphenyl) and titanium isopropoxide (2:1 molar ratio in dichloromethane/toluene).…”

mentioning

confidence: 99%

Quasi Solvent‐Free Enantioselective Carbonyl‐Ene Reaction with Extremely Low Catalyst Loading

Zhang

Ding

2003

Angew Chem Int Ed

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Asymmetric catalysis of organic reactions to provide enantiomerically enriched products is of central importance to modern synthetic and pharmaceutical chemistry.[1] The development of chiral catalysts for the enantioselective carboncarbon bond-forming reactions is a fundamental topic in asymmetric catalysis.[1] However, many currently accessible methods are impractical, for example, in terms of efficiency and environmental considerations.[2] Therefore the development of truly efficient and practical synthesis has been one of the greatest challenges for synthetic chemists. As part of our continuing effort in this area, [3] we report in this communication the first quasi solvent-free enantioselective carbonylene reaction. The reaction of ethyl glyoxylate with a variety of olefins could be carried out with 0.1-0.01 mol % of catalysts to give a-hydroxy esters in good to excellent yields and up to 99 % ee [Eq. (1)].For practical synthesis, solvent-free processes are ideal in terms of volumetric productivities and environmental safety.[4] Although most catalytic asymmetric processes are highly sensitive to the polarity of solvent and the concentration of substrates, a solvent-free procedure might be suitable for an asymmetric reaction with a concerted mechanism [3] because its transition state is less influenced by the polarity of the solvents. The thermal pericyclic ene reaction represents a typical concerted pathway involving six electrons with a suprafacial orbital interaction, [5] and its asymmetric version has been achieved with various chiral Lewis acids including Al, Ti, Ni, Pt, Pd, Yb, and Cu complexes. [6,7] The catalyst loadings employed in most cases were in the range from 1 to 10 mol %. In our experiments we employed binolate-Ti, which was prepared in situ by the reaction of (R)-binol (2,2'-dihydroxy-1,1'-biphenyl) and titanium isopropoxide (2:1 molar ratio in dichloromethane/toluene). Under nearly solvent-free conditions (the solvent volume from the catalyst was about 13 % of the whole system) and with a catalyst loading of 0.1 mol %, a-methylstyrene (1 a) reacted with ethyl glyoxylate (2) [Eq. (1)] efficiently at room temperature to give a-hydroxy ester (R)-3 a in quantitative yields and good enantioselectivity (90 % ee). The practical advantages of this strategy-the easy preparation of the catalyst, the nearly solvent-free conditions, the high yield and enantiopurity of the product, and the extremely low catalyst loading-make this protocol attractive for the preparation of enantiomerically enriched a-hydroxy esters of biological and synthetic importance.Tuning the sterics and electronics of the diol ligands in their metal complexes is essential to achieving highly efficient catalysts for asymmetric reactions, and the combinatorialchemistry approach may be a powerful strategy for this purpose.[8] We searched for more efficient catalysts for the reaction of 1 a with 2 by high-throughput screening of a catalyst library generated from the parallel combination of any two of the ligands shown in Scheme 1 with...

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“…Wulff and coworkers employed 2,2-diphenyl-4,4 -dihydroxy-3,3 -diphenanthryl (VAPOL) aluminum complex possessing a deeper pocket, and attained 97.8% ee with a turnover number of 200 253,254 . The asymmetric Claisen rearrangement of 1-trimethylsilylvinyl cinnamyl ether was promoted by 3,3 -bis(t-butyldiphenylsilylated) BINOL aluminum complex (equation 69) 255 , and the asymmetric ene-reaction of 2-phenylthiopropene and pentafluorobenzaldehyde by the triphenylsilyl derivative 256 . …”

Section: B Organic Synthesis Using Metal Complexes Of Biphenol: Binomentioning

confidence: 99%

Synthetic Uses of Phenols

Yamaguchi

2009

Patai's Chemistry of Functional Groups

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Asymmetric ene reaction catalyzed by chiral organoaluminum reagent

Cited by 157 publications

References 16 publications

Self‐Supported Heterogeneous Titanium Catalysts for Enantioselective Carbonyl–Ene and Sulfoxidation Reactions

Self‐Supported Heterogeneous Titanium Catalysts for Enantioselective Carbonyl–Ene and Sulfoxidation Reactions

Quasi Solvent‐Free Enantioselective Carbonyl‐Ene Reaction with Extremely Low Catalyst Loading

Synthetic Uses of Phenols

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