- Palladium(0)-catalyzed iminohalogenation of alkenes: Synthesis of 2-halomethyl dihydropyrroles and mechanistic insights into the alkyl halide bond formation
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Although the advances on carbon halide reductive elimination have been made, the alkyl bromide and chloride analogues remain a challenge. Here, a palladium(0)-catalyzed iminohalogenation of γ,δ-unsaturated oxime esters is described, and the use of electron-poor phosphine ligands proved to be crucial to promoting alkyl bromide and chloride reductive elimination. Furthermore, SN2-type alkyl bromide and chloride reductive elimination has also been established.
- Chen, Chen,Hou, Longlei,Cheng, Mian,Su, Jianhua,Tong, Xiaofeng
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- A Catalytic Enantioselective Iodocyclization Route to Dihydrooxazines
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The first catalytic enantioselective synthesis of 5,6-dihydro-4H-1,2-oxazines bearing an oxygen-containing quaternary stereogenic center has been developed through iodoetherification of γ,δ-unsaturated oximes. This operationally straightforward reaction i
- Suresh, Rahul,Simlandy, Amit Kumar,Mukherjee, Santanu
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- 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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p. 10005 - 10013
(2021/07/19)
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- Radical Aza-Cyclization of α-Imino-oxy Acids for Synthesis of Alkene-Containing N-Heterocycles via Dual Cobaloxime and Photoredox Catalysis
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Nitrogen-containing heterocycles are prevalent in both naturally and synthetically bioactive molecules. We report herein an unprecedented protocol for radical aza-cyclization of α-imino-oxy acids with pendant alkenes via synergistic photoredox and cobaloxime catalysis. With or without alkenes as the intermolecular cross-coupling partners, the transformation provides a variety of corresponding alkene-containing dihydropyrrole products in satisfactory yields. In the presence of external alkenes, the tandem reaction generates E-selective coupling products with excellent chemo- and stereoselectivity.
- Tu, Jia-Lin,Liu, Jia-Li,Tang, Wan,Su, Ma,Liu, Feng
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p. 1222 - 1226
(2020/02/15)
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- Iron-catalyzed acylation-functionalization of unactivated alkenes with aldehydes
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Herein, an iron-catalyzed acylation-functionalization of unactivated alkenes with aldehydes via distal group ipso-migration is reported. This strategy overcame the energy barrier and reversibility in the difunctionalization of unactivated alkenes with nuc
- Tian, Tian,Wang, Xin,Lv, Leiyang,Li, Zhiping
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p. 14637 - 14640
(2020/12/02)
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- Copper-Catalyzed Cope-Type Hydroamination of Nonactivated Olefins toward Cyclic Nitrones: Scope, Mechanism, and Enantioselective Process Development
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The catalytic synthesis of cyclic nitrones, an important type of functional molecules for both synthetic chemistry and related fields, remains underdeveloped. Herein we report the copper-catalyzed Cope-type hydroamination of oximes with pendant nonactivated olefins, which enables facile access to a series of five- and six-membered cyclic nitrones under mild conditions. In this study, heterocycle-tethered oximes were employed in the Cope-type hydroamination reaction for the first time. High enantioselectivity was achieved for carbon-tethered γ,δ-vinyl oximes to afford enantioenriched five-membered cyclic nitrones. The results of preliminary mechanistic studies indicate a mononuclear catalytic species and a unified catalytic pathway over a large temperature range.
- Zhang, Mengru,Liu, Shuang,Li, Hexin,Guo, Yajing,Li, Na,Guan, Meihui,Mehfooz, Haroon,Zhao, Jinbo,Zhang, Qian
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p. 12620 - 12627
(2019/09/16)
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- An Umpolung Approach to Alkene Carboamination: Palladium Catalyzed 1,2-Amino-Acylation, -Carboxylation, -Arylation, -Vinylation, and -Alkynylation
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Conventional approaches to Pd-catalyzed alkene 1,2-carboamination rely upon the combination of a nucleophilic nitrogen-based component and an internal C-based or external oxidant. In this study, we outline an umpolung approach, which is triggered by oxidative initiation at an electrophilic N-based component and employs "standard" organometallic nucleophiles to introduce the new carbon-based fragment. Specifically, oxidative addition of a Pd(0)-catalyst into the N-O bond of O-pentafluorobenzoyl oxime esters generates imino-Pd(II) intermediates, which undergo 5-exo cyclization with sterically diverse alkenes. The resultant alkyl-Pd(II) intermediates are intercepted by organometallic nucleophiles or alcohols, under carbonylative or noncarbonylative conditions, to provide 1,2-carboamination products. This approach provides, for the first time, a unified strategy for achieving alkene 1,2-amino-acylation, -carboxylation, -arylation, -vinylation, and -alkynylation. For carbonylative processes, orchestrated protodecarboxylation of the pentafluorobenzoate leaving group underpins reaction efficiency. This process is likely a key feature in related Narasaka-Heck cyclizations and accounts for the efficacy of O-pentafluorobenzoyl oxime esters in aza-Heck reactions of this type. (Chemical Equation Presented).
- Faulkner, Adele,Scott, James S.,Bower, John F.
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supporting information
p. 7224 - 7230
(2015/06/25)
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- Expedient Access to 2,3-Dihydropyridines from Unsaturated Oximes by Rh(III)-Catalyzed C-H Activation
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α,β-Unsaturated oxime pivalates are proposed to undergo reversible C(sp2)-H insertion with cationic Rh(III) complexes to furnish five-membered metallacycles. In the presence of 1,1-disubstituted olefins, these species participate in irreversible migratory insertion to give, after reductive elimination, 2,3-dihydropyridine products in good yields. Catalytic hydrogenation can then be used to convert these molecules into piperidines, which are important structural components of numerous pharmaceuticals.
- Romanov-Michailidis, Fedor,Sedillo, Kassandra F.,Neely, Jamie M.,Rovis, Tomislav
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supporting information
p. 8892 - 8895
(2015/08/03)
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- Pd-catalyzed domino carbonylative-decarboxylative allylation: An easy and selective monoallylation of ketones
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In the presence of an allyl alcohol, α-chloroacetophenones undergo an allyloxycarbonylation reaction followed by in situ decarboxylative allylation to selectively afford the corresponding monoallylated ketones via a Pd-catalyzed domino sequence. The scope of the reaction was extended to substituted α-chloroacetophenones as well as various allyl alcohols.
- Giboulot, Steven,Liron, Frederic,Prestat, Guillaume,Wahl, Benoit,Sauthier, Mathieu,Castanet, Yves,Mortreux, Andre,Poli, Giovanni
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supporting information; experimental part
p. 5889 - 5891
(2012/07/28)
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- Organoaluminum-Promoted Cyclization of Olefinic Epoxides. a New and Stereoselective Approach to Cyclohexane Frameworks
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A new, general synthetic method of six-membered carbocycles has been demonstrated, which involves the stereo-controlled cyclization of olefinic epoxides with methylaluminum bis(4-bromo-2,6-di-t-butylphenoxide) (MABR) via the epoxide rearrangement and subsequent intramolecular ene reaction with high stereoselectivity. This strategy is shown to be highly useful in the stereoselective synthesis of the basic skeleton of various terpenes.
- Murase, Noriaki,Maruoka, Keiji,Ooi, Takashi,Yamamoto, Hisashi
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p. 707 - 711
(2007/10/03)
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- Palladium-catalysed Synthesis of α-Diallylated Ketosulphides of Benzothiazole and their Transformation into Diallyl Thiiranes and Trienes
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α-Ketosulphides of benzothiazole 1 react with allylic carbonates in the presence of palladium acetate in dichloromethane under mild conditions affording α,α-diallylated ketosulphides 2 in high yields.Reduction of 2 with sodium borohydride in isopropanol gives episulphides which in turn can be transformed almost quantitatively into trienes.
- Calo, Vincenzo,Fiandanese, Vito,Nacci, Angelo,Scilimati, Antonio
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p. 171 - 174
(2007/10/02)
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- Cycloaddition reaction with the participation of unsaturated ketones catalyzed by an Rh(I)-Sn(II) system
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Codimerization of vinyl ketones with metallylacetone or metallylacetophenone in the presence of 2-SnCl2 affords substituted endo-2-acyl-8-oxabicyclooctanes, the products of the formal cycloaddition. - Key words: cycloaddition;
- Strelenko, Yu. A.,Ipatkin, V. V.,Kovalev, I. P.,Nikishin, G. I.
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p. 2187 - 2189
(2007/10/03)
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- A Mild Oxidation of 1,1-Diorganometallics to Ketones and Aldehydes. A New Stereoselective Approach to Aldol Products Part I
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The 1,1-diorganometallics of magnesium and zinc 1 are converted by the reaction with Me3SnCl to the 1,1-diorganometallics of tin and zinc 2 which are readily oxidized by dry air at -10 deg C to 0 deg C to afford the corresponding aldehydes and ketones 3 in 57-91percent yield.This mild oxidation reaction allows a new stereoselective approach to aldol products.An extension of the reaction to 1,1-diorganometallics of silicon and zinc is described.
- Knochel, Paul,Xiao, Chaodong,Yeh, Ming Chang P.
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p. 6697 - 6700
(2007/10/02)
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- Palladium-Catalyzed Decarboxylative Allylic Alkylation of Allylic Acetates with β-Keto Acids
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In the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium, β-keto acids react with allylic acetates at ambient temperature to produce α-allylic ketones in good yields with quantitative decarboxylation.This palladium-catalyzed decarboxylative allylic alkylation of allylic acetates with β-keto acids is characterized by high regio- and stereoselectivity.Allylation of β-keto acid takes place at the carbon atom bearing a carboxyl group.Allylic alkylation of allylic acetate with β-keto acid occurs at the less substituted end of the allyl group.The resultant carbon-carbon double bond of the α-allylic ketone has the E configuration.Allylic alkylation of lactone 25 with benzoylacetic acid proceeds preferably with retention of configuration, indicative of trans attack of the enolate on the (?-allyl)palladium intermediate from the opposite side of palladium even in the coexistence of free carboxylic acids.
- Tsuda, Tetsuo,Okada, Masahiro,Nishi, Sei-ichi,Saegusa, Takeo
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p. 421 - 426
(2007/10/02)
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- DIASTEREOSELECTION IN RHODIUM-MEDIATED INTRAMOLECULAR C-H INSERTION: PREPARATION OF A TRANS-3,4 DIALKYL CYCLOPENTANE
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Transition state analysis suggests that substantial 1,2 asymmetric induction could be observed in the course of rhodium-mediated intramolecular C-H insertion.This analysis succesfully predicts predominant formation of the trans 3,4-dialkyl cyclopentane wh
- Taber, Douglass F.,Ruckle, Robert E.
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p. 3059 - 3062
(2007/10/02)
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