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ABSTRACT: Just click with silver: Pyrroles are prepared by the co-cyclization of terminal alkynes and isocyanides in a silver-catalyzed click reaction. This protocol represents an extremely simple, efficient, and atom-economic approach to substituted pyrroles in good yields with high selectivity, thus complementing the click method for the rapid formation of multifunctional heterocycles.
Angewandte Chemie International Edition 04/2013; · 13.45 Impact Factor
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ABSTRACT: CHoose nickel: The nickel-catalyzed oxidative arylation of C(sp(3) )H bonds has been achieved. Several substituted arylboronic acids and various C(sp(3) )H bonds were found to be suitable substrates for this novel transformation, which is likely to proceed through a radical pathway. This method allows the introduction of simple ether derivatives to construct α-arylated ethers. FG=functional group.
Angewandte Chemie International Edition 03/2013; · 13.45 Impact Factor
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ABSTRACT: Through a nickel-catalysed Heck-type reaction, a direct coupling of alkenes with α-cyano alkyl bromides was achieved. This procedure provides a novel way for the synthesis of β,γ-unsaturated nitriles.
Chemical Communications 02/2013; 49(24):2442-4. · 6.17 Impact Factor
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ABSTRACT: In the past five years, visible-light mediated photoredox catalysis has been emerging as one of the fastest growing fields in organic chemistry because of its low cost, easy availability and environmental benignness. This review intends to summarize recent research progress in novel methodology development and application in organic synthesis, and is organized in terms of key reactive intermediates.
Organic & Biomolecular Chemistry 02/2013; · 3.70 Impact Factor
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ABSTRACT: Through the use of [Ru(bpy)(3) Cl(2) ] (bpy=2,2'-bipyridine) and [Ir(ppy)(3) ] (ppy=phenylpyridine) as photocatalysts, we have achieved the first example of visible-light photocatalytic radical alkenylation of various α-carbonyl alkyl bromides and benzyl bromides to furnish α-vinyl carbonyls and allylbenzene derivatives, prominent structural elements of many bioactive molecules. Specifically, this transformation is regiospecific and can tolerate primary, secondary, and even tertiary alkyl halides that bear β-hydrides, which can be challenging with traditional palladium-catalyzed approaches. The key initiation step of this transformation is visible-light-induced single-electron reduction of CBr bonds to generate alkyl radical species promoted by photocatalysts. The following carboncarbon bond-forming step involves a radical addition step rather than a metal-mediated process, thereby avoiding the undesired β-hydride elimination side reaction. Moreover, we propose that the Ru and Ir photocatalysts play a dual role in the catalytic system: they absorb energy from the visible light to facilitate the reaction process and act as a medium of electron transfer to activate the alkyl halides more effectively. Overall, this photoredox catalysis method opens new synthetic opportunities for the efficient alkenylation of alkyl halides that contain β-hydrides under mild conditions.
Chemistry 02/2013; · 5.93 Impact Factor
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ABSTRACT: AlCl(3) promoted Friedel-Crafts acylation between 4-tert-butylbenzoyl chloride and mesitylene was investigated. The donor-acceptor complex was observed as the major species. Kinetic investigation demonstrated that the reaction was first-order on the donor-acceptor complex and zero-order on ArH, suggesting that the donor-acceptor complex was not the true reactive species. However, the acylium ion was almost invisible with a fairly low concentration under live reaction conditions. It was approved as the true reactive species through kinetic data ("kinetic capture") in the AlCl(3) promoted Friedel-Crafts acylation reaction.
Organic & Biomolecular Chemistry 02/2013; · 3.70 Impact Factor
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ABSTRACT: Let's get radical: The first copper-catalyzed oxidative coupling of alkenes and aldehydes was developed. Various aldehydes were utilized as substrates to construct α,β-unsaturated ketones. A preliminary mechanistic study indicated that this reaction is likely to proceed through a single-electron transfer.
Angewandte Chemie International Edition 01/2013; · 13.45 Impact Factor
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ABSTRACT: The oxidant controlled palladium catalysed selective oxidation of primary alcohols to aldehydes or esters was investigated. The electronic properties of the benzylic alcohols and the structure of the oxidant are both important factors in controlling the selectivity between aldehydes and esters. A covalent benzyl ligand derived from BnCl provides η(3) coordination to the Pd centre. This covalent ligand is the key to the selective oxidative esterification of primary alcohols.
Chemical Communications 01/2013; · 6.17 Impact Factor
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ABSTRACT: Rate-limiting: The transmetalation step of the Sonogashira coupling reaction is established as the rate-limiting step. This cross-coupling is demonstrated to be a Pd-catalyzed and Cu-catalyzed synergistic process, which exhibits a first-order kinetic dependence on both the [Pd] and [Cu] catalysts.
Angewandte Chemie International Edition 12/2012; · 13.45 Impact Factor
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ABSTRACT: Insights toward the Cu-catalyzed C-C coupling reaction were investigated through operando IR and in situ XANES/EXAFS. It was found that the Cu(I)-complex formed from the reaction of CuI with beta-diketone nucleophile was liable under the cross-coupling conditions, which is usually considered as active catalytic species. This labile Cu(I)-complex could rapidly disproportionate to the spectator Cu(II) and Cu(0) species under the reaction conditions, which was an off-cycle process. In this copper-catalyzed C-C coupling reaction, beta-diketone might act both as the substrate and the ligand.
Journal of the American Chemical Society 12/2012; · 9.91 Impact Factor
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ABSTRACT: Different metalloporphyrin model compounds have been synthesized to study the mechanisms of cytochrome P450s with various terminal oxidants, and numerous intermediates have been reported. However, the detailed mechanism of the oxygen atom transfer from iodosylarene to the substrates remains unclear. Here we report the direct ultraviolet-visible spectroscopic observation of the soluble iodosylarene-manganese porphyrin adduct following catalytic oxidation using 2,4,6-tri-tert-butylphenol as the reductant. When the reductant is changed to cis-stilbene, the rate-determining step also changes. Both the iodosylarene-manganese porphyrin adduct and [(porphyrin)Mn(V)=O] species may be simultaneously observed. In the absence of reductant, the adduct of iodosylarene with sterically hindered [Mn(meso-tetrakis(2,6-dichlorophenyl)porphinato)Cl] is immediately formed, and smoothly converted into a high-valent [(porpyrinato)Mn=O]. Electrospray ionization mass spectrometry analysis of the reaction further confirms the transformation between these species. This study provides an insight into the mechanism of oxygen transfer within the haem-containing enzymatic systems.
Nature Communications 11/2012; 3:1190. · 7.40 Impact Factor
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ABSTRACT: Da-ddy, DDQ: By using catalytic amounts of DDQ combined with MnO(2) as oxidant, an efficient oxidative CO coupling of benzylic sp(3) CH bonds with carboxylic acids affords a series of carboxylic esters in 70-98 % yields. A wide range of functional groups and various carboxylic acids are tolerated. The reaction involves both CH functionalization and CO bond formation.
ChemSusChem 11/2012; · 6.83 Impact Factor
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ABSTRACT: Transitions: The title reaction has been developed for the synthesis of a variety of tert-butyl benzoates by employing 1,10-phenanthroline as an additive. Various functional groups were tolerated and heteroaryl iodides were also suitable substrates. Preliminary mechanism studies were conducted and indicate the participation of radical intermediates.
Angewandte Chemie International Edition 11/2012; · 13.45 Impact Factor
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ABSTRACT: A novel silver-mediated highly selective C-H/N-H oxidative cross-coupling/cyclization between 2-aminopyridines and terminal alkynes has been demonstrated. This approach provided a simple way to construct heteroaromatic imidazo[1,2-a]pyridines. By using this protocol, the marketed drug zolimidine (antiulcer) could be synthesized easily.
Chemical Communications 09/2012; 48(90):11073-5. · 6.17 Impact Factor
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ABSTRACT: Less is More: A highly selective Pd-catalyzed C(sp) -C(sp) cross-coupling reaction between terminal alkynes and 1-bromoacetylenes has been developed. Catalyst loading is low (only 0.0001-0.01 mol % of Pd is required) and provides products with high selectivities and good to excellent yields under mild conditions. TBAB=tetrabutylammonium bromide, TON=turnover number.
Angewandte Chemie International Edition 08/2012; 51(38):9547-51. · 13.45 Impact Factor
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ABSTRACT: The Negishi coupling has been widely applied in organic synthesis, while relevant mechanistic studies are relatively rare. To obtain an understanding of the fundamental steps in the Negishi coupling, oxidative addition, transmetalation and reductive elimination, the kinetic investigation has served as one of the most important strategies. In this review, insights into the elementary steps in the Negishi coupling through kinetic investigations are summarized.
Organic & Biomolecular Chemistry 07/2012; 10(34):6817-25. · 3.70 Impact Factor
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ABSTRACT: It's a benzyl kind of magic: In the title reaction proceeding with benzyl chloride as the oxidant the benzyl group serves as a carbon ligand, thus having an η(3) -coordination effect on palladium. A variety of aldehydes and alcohols were selectively converted into the corresponding esters in good to excellent yields.
Angewandte Chemie International Edition 04/2012; 51(23):5662-6. · 13.45 Impact Factor
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ABSTRACT: No pressure: The oxidation of aromatic CH bonds at room temperature was realized through a copper-catalyzed "oxygenase-type" oxidation of arenes and heteroarenes in the presence of air. The reaction involves an oxygen-atom transfer from O(2) in the air onto the substrates.
Angewandte Chemie International Edition 04/2012; 51(19):4666-70. · 13.45 Impact Factor
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ABSTRACT: Two at once: Xanthones with different functional groups were obtained with CO (balloon) in the presence of a simple catalytic system that consists of Pd(OAc)(2) , K(2) S(2) O(8) , and trifluoroacetic acid. Preliminary mechanism studies reveal that the second CH functionalization might be the rate-determining step.
Angewandte Chemie International Edition 04/2012; 51(21):5204-7. · 13.45 Impact Factor
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ABSTRACT: A novel silver-mediated highly selective oxidative C-H/C-H functionalization of 1,3-dicarbonyl compounds with terminal alkynes for the creation of polysubstituted furans and pyrroles in one step has been demonstrated. Promoted by the crucial silver species, perfect selectivity and good to excellent yields could be achieved. This protocol represents an extremely simple and atom-economic way to construct polysubstituted furans and pyrroles from basic starting materials under mild conditions.
Journal of the American Chemical Society 03/2012; 134(13):5766-9. · 9.91 Impact Factor
