- Carbonylative coupling of allylic acetates with aryl boronic acids
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The first allylic carbonylation reaction of allylic acetates with aryl boronic acids under carbon monoxide has been developed. Using Pd-PCy3 as a catalyst, a wide spectrum of allylic acetates was carbonylated in the presence of various aryl boronic acids, affording α,β-unsaturated aryl ketones in good to excellent yields. Preliminary studies indicate that carbon monoxide always inserts at the least substituted terminal allylic carbon and the resulting β,γ-unsaturated aryl ketones generally isomerise to the ketones obtained.
- Ma, Wei,Xue, Dong,Yu, Ting,Wang, Chao,Xiao, Jianliang
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- Catalytic Dynamic Kinetic Resolutions in Tandem to Construct Two-Axis Terphenyl Atropisomers
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The defined structure of molecules bearing multiple stereogenic axes is of increasing relevance to materials science, pharmaceuticals, and catalysis. However, catalytic enantioselective approaches to control multiple stereogenic axes remain synthetically challenging. We report the catalytic synthesis of two-axis terphenyl atropisomers, with complementary strategies to both chlorinated and brominated variants, formed with high diastereo-and enantioselectivity. The chemistry proceeds through a sequence of two distinct dynamic kinetic resolutions: first, an atroposelective ring opening of Bringmann-type lactones produces a product with one established axis of chirality, and second, a stereoselective arene halogenation delivers the product with the second axis of chirality established. In order to achieve these results, a class of Br?nsted basic guanidinylated peptides, which catalyze an efficient atroposelective chlorination, is reported for the first time. In addition, a complementary bromination is reported, which also establishes the second stereogenic axis. These bromo-terphenyls are accessible following the discovery that chiral anion phase transfer catalysis by C2-symmetric phosphoric acids allows catalyst control in the second stereochemistry-determining event. Accordingly, we established the fully catalyst-controlled stereodivergent synthesis of all possible chlorinated stereoisomers while also demonstrating diastereodivergence in the brominated variants, with significant levels of enantioselectivity in all cases.
- Beleh, Omar M.,Miller, Edward,Toste, F. Dean,Miller, Scott J.
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- Synthesis of Z-alkenes from Rh(I)-catalyzed olefin isomerization of β,γ-unsaturated ketones
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Developing olefin isomerization reactions to reach kinetically controlled Z-alkenes is challenging because formation of trans-alkenes is thermodynamically favored under the traditional catalytic conditions using acids, bases, or transition metals as the catalysts. A new synthesis of Z-alkenes from Rh(I)-catalyzed olefin isomerization of β,γ-unsaturated ketones to α,β-unsaturated ketones was developed, providing an easy and efficient way to access various Z-enones.
- Zhuo, Lian-Gang,Yao, Zhong-Ke,Yu, Zhi-Xiang
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p. 4634 - 4637
(2013/10/08)
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- Asymmetric hydrocyanation of α,β-unsaturated ketones into β-cyano ketones with the [Ru(phgly)2(binap)]/C6H 5OLi catalyst system
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Enantioselective conjugate addition of HCN to α,β-unsaturated ketones catalyzed by the combined system of [Ru{(S)-phgly}2{(S)- binap}] and C6H5OLi has afforded β-cyano ketones in high yield (see scheme). No detectable amount of the corresponding 1,2-adduct was produced and tert-C4H9OCH3 was the solvent of choice. The cyanation was conducted with a substrate-to-catalyst molar ratio in the range of 200:1-1000:1 at -20-0°C. Copyright
- Kurono, Nobuhito,Nii, Noriyuki,Sakaguchi, Yusuke,Uemura, Masato,Ohkuma, Takeshi
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supporting information; experimental part
p. 5541 - 5544
(2011/07/08)
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