- Oxidative Cleavage of Alkenes by O2with a Non-Heme Manganese Catalyst
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The oxidative cleavage of C═C double bonds with molecular oxygen to produce carbonyl compounds is an important transformation in chemical and pharmaceutical synthesis. In nature, enzymes containing the first-row transition metals, particularly heme and non-heme iron-dependent enzymes, readily activate O2 and oxidatively cleave C═C bonds with exquisite precision under ambient conditions. The reaction remains challenging for synthetic chemists, however. There are only a small number of known synthetic metal catalysts that allow for the oxidative cleavage of alkenes at an atmospheric pressure of O2, with very few known to catalyze the cleavage of nonactivated alkenes. In this work, we describe a light-driven, Mn-catalyzed protocol for the selective oxidation of alkenes to carbonyls under 1 atm of O2. For the first time, aromatic as well as various nonactivated aliphatic alkenes could be oxidized to afford ketones and aldehydes under clean, mild conditions with a first row, biorelevant metal catalyst. Moreover, the protocol shows a very good functional group tolerance. Mechanistic investigation suggests that Mn-oxo species, including an asymmetric, mixed-valent bis(μ-oxo)-Mn(III,IV) complex, are involved in the oxidation, and the solvent methanol participates in O2 activation that leads to the formation of the oxo species.
- Bennett, Elliot L.,Brookfield, Adam,Guan, Renpeng,Huang, Zhiliang,Mcinnes, Eric J. L.,Robertson, Craig M.,Shanmugam, Muralidharan,Xiao, Jianliang
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supporting information
p. 10005 - 10013
(2021/07/19)
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- MOF-808 as a recyclable catalyst for the photothermal acetalization of aromatic aldehydes
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Metal-organic frameworks (MOFs) show promise for catalysis applications due to their porosity, high internal surface area, and structural adaptability. Typical acetylation reactions of aldehydes require elevated temperatures and excess alcohol to drive the reactions to completion. In this current work, MOF-808 is used as a heterogeneous catalyst for acetylation of aldehydes in methanol using a mild photothermal process. Optimized conditions gave 72% yield of 2-(dimethoxymethyl)naphthalene in the presence of 10 mol% MOF-808 at 45 °C using only a fluorescent lamp. MOF-808 can be recycled up to 5 times with no loss in catalytic activity. A proof-of-principle substrate scope demonstrates the potential utility for aromatic and aliphatic substrates.
- Rabon, Allison M.,Doremus, Jared G.,Young, Michael C.
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supporting information
(2021/04/02)
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- A recyclable fluorous hydrazine-1,2-bis(carbothioate) with NCS as efficient catalysts for acetalization of aldehydes
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A fluorous hydrazine-carbothioate organocatalyst was prepared. Together with NCS, the catalyst showed a good activity in acetalization of aldehydes and alcohols. It could be recovered from the reaction mixture by fluorous solid-phase extraction (F-SPE) with excellent purity for direct reuse.
- Zhu, Yi-Wei,Yi, Wen-Bin,Cai, Chun
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supporting information
p. 890 - 892
(2013/07/05)
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- Direct conversion of acetals to esters with high regioselectivity via O,P-acetals
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A new direct conversion of O,O-acetals to esters via O,P-acetal intermediates was developed. The regioselective cleavage of unsymmetrical cyclic acetals occurred to give the more crowded esters as single isomers.
- Maegawa, Tomohiro,Otake, Kazuki,Goto, Akihiro,Fujioka, Hiromichi
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supporting information; experimental part
p. 5648 - 5651
(2011/09/15)
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- An unusual reaction of α-alkoxyphosphonium salts with Grignard reagents under an O2 atmosphere
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An unusual and novel reaction of α-alkoxyphosphonium salts, generated from O,O-acetals and Ph3P, with Grignard reagents under an O 2 atmosphere afforded alcohols in moderate to high yields. It was clarified by isotopic labelling experiments that the reaction proceeded via a novel radical pathway.
- Fujioka, Hiromichi,Goto, Akihiro,Otake, Kazuki,Kubo, Ozora,Sawama, Yoshinari,Maegawa, Tomohiro
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supporting information; experimental part
p. 9894 - 9896
(2011/10/09)
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- Remarkable effect of phosphine on the reactivity of O,P-acetal - Efficient substitution reaction of O,P-acetal
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The structure and electronic nature of the phosphine have a significant influence on not only the formation, but also the subsequent transformation of O,P-acetals. The O,P-acetals generated from tris(o-tolyl)phosphine [(o-tol) 3P] underwent efficient substitution reactions with various nucleophiles.
- Fujioka, Hiromichi,Goto, Akihiro,Otake, Kazuki,Kubo, Ozora,Yahata, Kenzo,Sawama, Yoshinari,Maegawa, Tomohiro
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supporting information; experimental part
p. 3976 - 3978
(2010/08/13)
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- NCS with thiourea as highly efficient catalysts for acetalization of aldehydes
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NCS/thiourea-mediated acetalization of aldehydes and alcohols has rapidly provided acetals in almost quantitative yields.
- Mei,Bentley,Du
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supporting information; experimental part
p. 4199 - 4200
(2009/10/04)
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- Carbon tetrabromide/sodium triphenylphosphine-m-sulfonate (TPPMS) as an efficient and easily recoverable catalyst for acetalization and tetrahydropyranylation reactions
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A solid complex, conveniently prepared from carbon tetrabromide and sodium triphenylphos-phine-m-sulfonate (TPPMS), can be used as an easily recoverable catalyst for the selective acetalization of aldehydes and tetrahydropyranylation of alcohols. The catalyst can be recovered by simple pre-cipitation with ether and can be reused at least 7 times without loss of catalytic activity.
- Huo, Congde,Chan, Tak Hang
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experimental part
p. 1933 - 1938
(2011/02/28)
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- Photochemical acetalization of carbonyl compounds in protic media using an in situ generated photocatalyst
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Carbonyl compounds are conveniently converted into their corresponding dimethyl acetals in good yields and short reaction times by means of a photochemical reaction in methanol with a catalytic amount of chloranil (2,3,5,6-tetrachloro-1,4-benzoquinone, CA) as the sensitizer. Using aldehydes gives better results than using ketones, which also tend to form enol ethers as side products. These results are similar to those of simple acid-catalyzed acetalization reactions, suggesting the involvement of a photochemically generated acid. On the basis of steady state and laser flash photolysis data the reaction is proposed to involve the in situ generation of a photocatalyst (2,3,5,6-tetrachloro-1,4-hydroquinone, TCHQ) via reaction of CA with the solvent. The acetalization process is initiated by ionization of TCHQ, followed by loss of a proton to the solvent or the carbonyl, which starts a catalytic reaction. The photocatalyst is regenerated via a disproportionation reaction.
- De Lijser, H.J. Peter,Rangel, Natalie Ann
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p. 8315 - 8322
(2007/10/03)
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- Efficient isomerization of allylic alcohols to saturated carbonyl compounds by activated rhodium and ruthenium complexes
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A range of readily available rhodium complexes of the general structures Rh(PPh3)3+ PF6- and RhX(PPh3)3 (X = H, Me, Ph) have been prepared and used in situ for the isomerization of allylic alcohols to their corresponding saturated carbonyl compounds. The isomerization of octen-3-ol, selected as a model, yielded octan-3-one in good yield. This reaction has been extended to the corresponding ruthenium complexes of the general structures [RuCl(PPh3)3]+ PF6-, RuXCl(PPh3)3 and RuX2(PPh3)3 (X = H, Me, Ph). It is noteworthy that many of these complexes have not been employed previously for this isomerization. The scope and efficiency of the process has been demonstrated by four representative complexes [RhH(PPh3)3, RuH2(PPh3)3, RuPh2(PPh3)3, RuCl(PPh3)3+ PF6-] with a wide variety of allylic alcohols. The reaction of primary allylic alcohols in the presence of RuCl(PPh3)3+ PF6- in methanol yields aldehydes protected as their methyl acetals. Deuterium labelling experiments are in agreement with a 1,3-hydride shift mechanism.
- Uma, Ramalinga,Davies, Maxwell K.,Crevisy, Christophe,Gree, Rene
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p. 3141 - 3146
(2007/10/03)
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- Functional transformation of aldehydes and ketones via homolytic induced decomposition of unsaturated peroxy acetals and peroxy ketals
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Induced decomposition of unsaturated peroxy acetals prepared from trimethyl orthoformate, dodecanal or 2-methyl-undecanal and 2,3-dimethyl-2-hydroperoxybut-3-ene, in the presence of ethyl iodoacetate, CC14 or dodecanethiol, allowed respectively their iodo-, chloro- and hydro-decarbonylation with yields of over 70%; the same reaction applied to the monoperoxy ketal or diperoxy ketal of cyclohexanone in the presence of ethyl iodoacetate resulted in its functional transformation in methyl 6-iodohexanoate or 1,5-diiodopentane with respective yields of 65 and 40%.
- Moutet,Bonafoux,Degueil-Castaing,Maillard
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p. 139 - 140
(2007/10/03)
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- Acid-catalyzed solvolysis of polyenol ethers. III. Effect of the alkoxy moiety
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The dependence of the solvolysis of polyenol ethers on the nature of the alkoxy moiety has been studied. A new reaction path, leading to the formation of ω-hydroxy (methoxy) substituted aldehydes and -esters, was established. The proposed reaction pathway (scheme 6) is initiated by an electron transfer from the polyenol ether to molecular oxygen, followed by combination of the two radicals to a peroxide zwitterion. Upon protonation, solvent adds to the ω-carbon atom of the polyene to give an intermediate that can either loose water to form an ester, or loose the alkoxy moiety to give an aldehyde. This mechanism is believed to be involved in the strong mutagenic activity displayed by many polyenol ethers, including the natural mutagen fecapentaene-12.
- Nieuwenhuis, Saskia A. M.,Vertegaal, Louis B. J.,De Zoete, Marian C.,Van Der Gen, Arne
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p. 13207 - 13230
(2007/10/02)
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- Acid-catalyzed solvolysis of polyenol ethers. II. Effect of the degree of unsaturation
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The acid-catalyzed solvolysis of polyenol ethers of glycerol gradually changes with increasing unsaturation from the regular pattern into an anomalous one in which hydroxy- and methoxy-substituted aldehydes are formed.
- Vertegaal,Van Der Gen
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p. 7301 - 7312
(2007/10/02)
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