- Visible-Light-Enabled Carboxylation of Benzyl Alcohol Derivatives with CO2 Using a Palladium/Iridium Dual Catalyst
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A highly efficient carboxylation of benzyl alcohol derivatives with CO2 using a palladium/iridium dual catalyst under visible-light irradiation was developed. A wide range of benzyl alcohol derivatives could be employed to provide benzylic carboxylic acids in moderate to high yields. Mechanistic studies indicated that the oxidative addition of benzyl alcohol derivatives was possibly the rate-determining-step. It was also found that a switchable site-selective carboxylation between benzylic C?O and aryl C?Cl moieties could be achieved simply by changing the palladium catalyst.
- Iwasawa, Nobuharu,Jin, Yushu,Toriumi, Naoyuki
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- Visible-Light-Driven External-Reductant-Free Cross-Electrophile Couplings of Tetraalkyl Ammonium Salts
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Cross-electrophile couplings between two electrophiles are powerful and economic methods to generate C-C bonds in the presence of stoichiometric external reductants. Herein, we report a novel strategy to realize the first external-reductant-free cross-electrophile coupling via visible-light photoredox catalysis. A variety of tetraalkyl ammonium salts, bearing primary, secondary, and tertiary C-N bonds, undergo selective couplings with aldehydes/ketone and CO2. Notably, the in situ generated byproduct, trimethylamine, is efficiently utilized as the electron donor. Moreover, this protocol exhibits mild reaction conditions, low catalyst loading, broad substrate scope, good functional group tolerance, and facile scalability. Mechanistic studies indicate that benzyl radicals and anions might be generated as the key intermediates via photocatalysis, providing a new direction for cross-electrophile couplings.
- Liao, Li-Li,Cao, Guang-Mei,Ye, Jian-Heng,Sun, Guo-Quan,Zhou, Wen-Jun,Gui, Yong-Yuan,Yan, Si-Shun,Shen, Guo,Yu, Da-Gang
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p. 17338 - 17342
(2019/01/04)
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- Ruthenium-catalyzed umpolung carboxylation of hydrazones with CO2
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The first ruthenium-catalyzed umpolung carboxylation of hydrazones with CO2 to generate important aryl acetic acids is reported. Besides aldehyde hydrazones, a variety of ketone hydrazones, which have not been successfully applied in previous umpolung reactions with other reactive electrophiles, also show high reactivity and selectivity under mild conditions. Moreover, this operationally simple protocol features good functional group tolerance, is readily scalable, and offers easy derivation of important structures, including bioactive felbinac and adiphenine. Computational studies reveal that this umpolung reaction proceeds through the generation of a Ru-nitrenoid followed by concerted [4 + 2] cycloaddition with CO2.
- Yan, Si-Shun,Zhu, Lei,Ye, Jian-Heng,Zhang, Zhen,Huang, He,Zeng, Huiying,Li, Chao-Jun,Lan, Yu,Yu, Da-Gang
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p. 4873 - 4878
(2018/06/07)
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- Mechanistic rationalization of unusual kinetics in Pd-catalyzed C-H olefination
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Detailed kinetic studies and novel graphical manipulations of reaction progress data in Pd(II)-catalyzed olefinations in the presence of mono-N-protected amino acid ligands reveal anomalous concentration dependences (zero order in o-CF3-phenylacetic acid concentration, zero order in oxygen pressure, and negative orders in both olefin and product concentrations), leaving the catalyst concentration as the sole positive driving force in the reaction. NMR spectroscopic studies support the proposal that rate inhibition by the olefinic substrate and product is caused by formation of reversible off-cycle reservoirs that remove catalyst from the active cycle. NMR studies comparing the interaction between the catalyst and substrate in the presence and absence of the ligand suggest that weak coordination of the ligand to Pd prevents formation of an inactive mixed acetate species. A fuller understanding of these features may lead to the design of more efficient Pd(II) catalysts for this potentially powerful C-H functionalization reaction.
- Baxter, Ryan D.,Sale, David,Engle, Keary M.,Yu, Jin-Quan,Blackmond, Donna G.
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supporting information; experimental part
p. 4600 - 4606
(2012/04/23)
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- An efficient method for one-carbon elongation of aryl aldehydes via their dibromoalkene derivatives
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Various aryl aldehydes were efficiently converted into one-carbon extended aryl acetamides or aryl acetic acids through the reaction of their dibromoalkene derivatives with pyrrolidine in the presence of water under very mild conditions.
- Huh, Dal Ho,Jeong, Ji Sang,Lee, Hee Bong,Ryu, Hoejin,Kim, Young Gyu
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p. 9925 - 9932
(2007/10/03)
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- N-acyl sulfamic acid esters (or thioesters), N-acyl sulfonamides, and N-sulfonyl carbamic acid esters (or thioesters) as hypercholesterolemic agents
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The present invention is directed to compounds useful for the regulation of cholesterol of Formula I, methods for using them and pharmaceutical compositions thereof, STR1 wherein X and Y are oxygen, sulfur, or (CR'R")n wherein n is 1 to 4; R is hydrogen, alkyl, or benzyl; R1 and R2 are phenyl, substituted phenyl, naphthyl, substituted naphthyl, an aralkyl group, an alkyl chain, adamantyl, or a cycloalkyl group.
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