- 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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- Photo-organocatalytic synthesis of acetals from aldehydes
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A mild and green photo-organocatalytic protocol for the highly efficient acetalization of aldehydes has been developed. Utilizing thioxanthenone as the photocatalyst and inexpensive household lamps as the light source, a variety of aromatic and aliphatic aldehydes have been converted into acyclic and cyclic acetals in high yields. The reaction mechanism was extensively studied.
- Nikitas, Nikolaos F.,Triandafillidi, Ierasia,Kokotos, Christoforos G.
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supporting information
p. 669 - 674
(2019/02/14)
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- Copper-Mediated, Palladium-Catalyzed Coupling of Thiol Esters with Aliphatic Organoboron Reagents
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Thiol esters and B-alkyl-9-BBN derivatives couple in the presence of a copper(I) carboxylate mediator and a palladium catalyst. In contrast to copper-mediated, palladium-catalyzed cross-couplings of thioorganics with boronic acids, the current coupling reaction of 9-BBN derivatives is facilitated by the addition of a base such as Cs2CO3. Under optimized conditions, a variety of thiol esters react with different B-alkyl-9-BBN derivatives giving ketones in moderate to excellent yields.
- Yu, Ying,Liebeskind, Lanny S.
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p. 3554 - 3557
(2007/10/03)
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- The mechanism of directed remote asymmetric reduction of carbonyl groups via homochiral boronate esters
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In order to determine whether the remote asymmetric induction in the reduction of compounds such as 1 and 2 using borane is really controlled by intramolecular chelates of type 3, rather than dioxaborolane oxygenborane chelates of type 12, a study was undertaken to examine related reductions involving the corresponding homochiral acetal 30 and comparative reductions of the dioxaborolane 14 and the acetal 23b.While this study showed that reductions of the dioxaborolane 14 and the acetal 23b with borane and L-Selectride were virtually identical, this result did not necessarily indicate that dioxaborolane oxygens or acetal oxygens were directing borane reduction.However, that the more likely explanation for the remote asymmetric induction observed for 1 and 2 being mediated by complex 3 was confirmed by the fact that the acetal 30 gave no asymmetric induction with borane.A crystal structure of the phenylboronate ester 10 has been carried out.
- Conole, Grainne,Mears, Richard J.,Silva, Harshani De,Whiting, Andrew
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p. 1825 - 1836
(2007/10/02)
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- Neighboring group participation in Lewis acid-promoted [3 + 4] and [3 + 5] annulations. The synthesis of oxabicyclo[3.n.1]alkan-3-ones
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Lewis acids are employed as catalysts in the annulation of 1,4- and 1,5-dicarbonyl dielectrophiles with bis(trimethylsilyl) end ethers of β-diketones and β-keto esters. A variety of 2-(alkoxycarbonyl)-m-oxabicyclo[3.n.1]alkan-3-ones can be constructed by this process in which two new carbon-carbon bonds are generated. Unusually high regiocontrol is observed, and good to excellent stereochemical control can be achieved at virtually every position on the new carbocycles. Intramolecular neighboring group participation is proposed to explain the unusually high selectivities attained in the annulation reaction.
- Molander, Gary A.,Camera, Kimberly O.
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p. 830 - 846
(2007/10/02)
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- THE PRODUCTION OF DIMETHYL ACETALS OF γ-KETOALDEHYDES FROM ALKYL AND ARYL 2-CHLOROCYCLOPROPYL KETONES
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In reaction with sodium methoxide in methanol alkyl and aryl 2-chlorocyclopropyl ketones are converted into the dimethyl acetals of γ-ketoaldehydes with yields of 75-85percent through the intermediate formation of 2-methoxycyclopropyl ketones.
- Kulinkovich, O. G.,Tischenko, I. G.,Sorokin, V. L.
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p. 2319 - 2323
(2007/10/02)
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