- Enantioselective formation of all-carbon quaternary stereocenters from indoles and tertiary alcohols bearing a directing group
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Described is an efficient catalytic asymmetric intermolecular C-C bond-formation process to generate acyclic all-carbon quaternary stereocenters. The reactions overcome the unfavorable steric hindrance around reactive centers, and the competitive elimination (E1), to form a range of useful indole products with excellent efficiency and enantioselectivity.
- Zhao, Wanxiang,Wang, Zhaobin,Chu, Boyang,Sun, Jianwei
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- A Metal-Organic Framework Br?nsted Acid Catalyst: Synthesis, Characterization and Application to the Generation of Quinone Methides for [4+2] Cycloadditions
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A Br?nsted acid-derived metal-organic framework (MOF) has been developed to serve as an efficient heterogeneous catalyst for a [4+2] cycloaddition. Aromatic sulfonyl groups were successfully installed using commercially available anhydridic reagents during post-synthetic modifications. The MIL-101-NH-RSO3H MOF catalyst was fully characterized by SEM, PXRD, FTIR, TGA and N2adsorption/desorption isotherm. Furthermore, a novel [4+2] cycloaddition of substituted 2-vinyl-substituted phenol was evaluated. The MIL-101-NH-RSO3H catalyst showed superior catalytic capabilities when compared to a few other strong homogeneous Br?nsted acid catalysts. The MIL-101-NH-RSO3H catalyst is compatible with a variety of substituted substrates and it can be recycled five times without loss of yield or selectivity. (Figure presented.).
- Qi, Chao,Ramella, Daniele,Wensley, Allison M.,Luan, Yi
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supporting information
p. 2604 - 2611
(2016/09/03)
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- Organocatalytic asymmetric synthesis of 1,1-diarylethanes by transfer hydrogenation
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A new organocatalytic transfer hydrogenation strategy for the asymmetric synthesis of 1,1-diarylethanes is described. Under mild conditions, a range of 1,1-diarylethanes substituted with an o-hydroxyphenyl or indole unit could be obtained with excellent efficiency and enantioselectivity. We also extended the protocol to an unprecedented asymmetric hydroarylation of 1,1-diarylalkenes with indoles for the synthesis of a range of highly enantioenriched 1,1,1-triarylethanes bearing acyclic all-carbon quaternary stereocenters. These diaryl- and triarylethanes exhibit impressive cytotoxicity against a number of human cancer cell lines. Preliminary mechanistic studies combined with DFT calculations provided important insight into the reaction mechanism.
- Wang, Zhaobin,Ai, Fujin,Wang, Zheng,Zhao, Wanxiang,Zhu, Guangyu,Lin, Zhenyang,Sun, Jianwei
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supporting information
p. 383 - 389
(2015/01/30)
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- OH-directed alkynylation of 2-vinylphenols with ethynyl benziodoxolones: A fast access to terminal 1,3-enynes
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The first direct alkynylation of 2-vinylphenols was developed. The rationally optimized hypervalent iodine reagent TIPS-EBX in combination with [(CpRhCl2)2] as a C-H-activating transition metal catalyst enables the construction of a variety of highly substituted 1,3-enynes in high yields of up to 98 %. This novel C-H activation method shows excellent chemoselectivity and exclusive (Z)-stereoselectivity, and it is also remarkably mild and tolerates a variety of functional groups. Furthermore, synthetic modifications of the resulting 1,3-enynes were demonstrated. To our knowledge, this is the first example for an OH-directed C-H alkynylation with hypervalent iodine reagents.
- Finkbeiner, Peter,Kloeckner, Ulrich,Nachtsheim, Boris J.
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supporting information
p. 4949 - 4952
(2015/04/14)
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- Palladium(II)-catalyzed direct carboxylation of alkenyl C-H bonds with CO2
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Pd-catalyzed direct carboxylation of alkenyl C-H bonds with carbon dioxide was realized for the first time. Treatment of 2-hydroxystyrenes and a catalytic amount of Pd(OAc)2 with Cs2CO3 under atmospheric pressure of CO2 afforded corresponding coumarins in good yield. Furthermore, isolation of the key alkenylpalladium intermediate via C-H bond cleavage was achieved. The reaction was proposed to undergo reversible nucleophilic addition of the alkenylpalladium intermediate to CO2.
- Sasano, Kota,Takaya, Jun,Iwasawa, Nobuharu
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supporting information
p. 10954 - 10957
(2013/08/23)
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