- Enhancing the photo-efficacy of an organic visible-light-activated chromophore (alizarin red S) on zinc oxide with a Ag-Na electrolyte to photo-transform aromatic and aliphatic alcohols
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The development of an aqueous silver-sodium/alizarin red sensitised zinc oxide system has been reported to oxidise a range of both aromatic and aliphatic alcohols to aldehydes. Furthermore, photoluminescence spectroscopy validated the electron quenching effect of zinc oxide's defect sites after surface sensitising the metal-oxide with alizarin red. Powder diffuse reflectance UV/Vis data further substantiated the visible-light attenuated properties of alizarin red sensitised zinc oxide, and hence justification for its visible light reactivity towards alcohol oxidations. Lastly, density functional theory calculations supported the intermolecular photo-electronic transfer between alizarin red organic and zinc oxide.
- Underwood, Timothy M.,Robinson, Ross S.
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- Enantioselective Organocatalytic Synthesis of 1,2,3-Trisubstituted Cyclopentanes
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An organocatalytic asymmetric domino Michael/α-alkylation reaction between enals and non-stabilized alkyl halides has been developed. Chiral secondary amine catalyzed cyclization reaction of 1-bromo-3-nitropropane with α,β-unsaturated aldehydes provides 1,2,3-trisubstituted cyclopentane carbaldehydes with high diastereo- (dr up to 8 : 1) and enantioselectivities (ee up to 96 %).
- ?otolová, Martina,Kamlar, Martin,Reme?, Marek,Géant, Pierre-Yves,Císa?ová, Ivana,?tícha, Martin,Vesely, Jan
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p. 5080 - 5089
(2021/09/30)
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- Stable gold(III) catalysts by oxidative addition of a carbon-carbon bond
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Low-valent late transition-metal catalysis has become indispensable to chemical synthesis, but homogeneous high-valent transition-metal catalysis is underdeveloped, mainly owing to the reactivity of high-valent transition-metal complexes and the challenges associated with synthesizing them. Here we report a carbon-carbon bond cleavage at ambient conditions by a Au(i) complex that generates a stable Au(iii) cationic complex. In contrast to the well-established soft and carbophilic Au(i) catalyst, this Au(iii) complex exhibits hard, oxophilic Lewis acidity. For example, we observed catalytic activation of α,β-unsaturated aldehydes towards selective conjugate additions as well as activation of an unsaturated aldehyde-allene for a [2 + 2] cycloaddition reaction. The origin of the regioselectivity and catalytic activity was elucidated by X-ray crystallographic analysis of an isolated Au(iii)-activated cinnamaldehyde intermediate. The concepts revealed suggest a strategy for accessing high-valent transition-metal catalysis from readily available precursors.
- Wu, Chung-Yeh,Horibe, Takahiro,Jacobsen, Christian Borch,Toste, F. Dean
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p. 449 - 454
(2015/03/04)
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- Combined heterogeneous metal/chiral amine: Multiple relay catalysis for versatile eco-friendly synthesis
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Herein is described a versatile and broad synergistic strategy for expansion of chemical space and the synthesis of valuable molecules (e.g. carbocycles and heterocycles), with up to three quaternary stereocenters, in a highly enantioselective fashion from simple alcohols (31 examples, 95:5 to >99.5:0.5 e.r.) using integrated heterogeneous metal/chiral amine multiple relay catalysis and air/O2 as the terminal oxidant. A novel highly 1,4-selective heterogeneous metal/amine co-catalyzed hydrogenation of enals was also added to the relay catalysis sequences. Relay switch: A versatile strategy for expansion of chemical space and the synthesis of valuable molecules, having up to three quaternary stereocenters, in a highly enantioselective fashion from simple alcohols is described. The method employs integrated heterogeneous metal/chiral amine multiple relay catalysis and air/O2 as the terminal oxidant.
- Deiana, Luca,Jiang, Yan,Palo-Nieto, Carlos,Afewerki, Samson,Incerti-Pradillos, Celia A.,Verho, Oscar,Tai, Cheuk-Wai,Johnston, Eric V.,C?rdova, Armando
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supporting information
p. 3447 - 3451
(2014/04/03)
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- Synthesis of α,β-unsaturated aldehydes and methyl carboxylic esters from 2-acetylenic phenyl sulfides
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2-Alkynylthio benzenes were reduced to 2-Alkenylthio benzenes with diisobutyl aluminum hydride. Mono chlorination of these compounds with sulfuryl chloride and pyridine followed by hydrolysis, in the presence of Cu(II) salts, gave α,β-unsaturated aldehydes. 2-Alkynylthio benzenes were converted into 2-Alkynyl 1,1-bis thiobenzenes by monochlorination with sulfuryl chloride and pyridine followed by treatment with thiophenol and triethylamine. These substances were then converted to α,β-unsaturated methyl carboxylic esters by way of isomerization with sodium methoxide to the corresponding allene and treatment with hydrochloric acid and methanolysis in the presence of iodine.
- Fortes, Carlos C.,Garrote, Clevia F. D.
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p. 3917 - 3941
(2007/10/03)
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- AN EFFICIENT REAGENT FOR SYNTHESIS OF α,β-UNSATURATED ALDEHYDES 3-METHYLTHIO-2-PROPENYL p-TOLYL SULFONE
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Alkylation of 3-methylthio-2-propenyl p-tolyl sulfone (1) with an alkyl halide and a base (NaH or KOH-TOMAC) took place at the position α to the sulfonyl group to give optionally a mono- or dialkylated product (2 or 3), which was converted to β-monosubstituted or β,β-disubstituted α,β-unsaturated aldehyde (6 or 7), respectively, by TiCl4-assisted hydrolysis followed by the removal of p-toluenesulfinic acid.
- Ogura, Katsuyuki,Iihama, Teruyuki,Takahashi, Kazumasa,Iida, Hirodata
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p. 2671 - 2674
(2007/10/02)
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