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Base-free Conditions (base-free + condition)

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Chemistry100%

Selected Abstracts

Nickel Complexes of N/O -Functionalized N-Heterocyclic Carbenes as Precatalysts for Michael Reactions in Air at Room Temperature Under the Much Preferred Base-Free Conditions

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2009
Sriparna Ray
Abstract A series of several new nickel precatalysts supported overN/O -functionalized N-heterocyclic carbenes (NHC) for the Michael reactions of ,-dicarbonyl, ,-keto ester, ,-diester, and ,-cyano ester compounds with ,,,-unsaturated carbonyl compounds in air at ambient temperature under the much preferred base-free conditions are reported. Specifically, the nickel complexes, [1-(R1 -aminocarbonylmethyl)-3-R2 -imidazol-2-ylidene]2Ni [R1 = 2-C6H4(OMe); R2 = Me (1b), iPr (2b), CH2Ph (3b) and R1 = 2-CH2C4H3O; R2 = Me (4b), CH2Ph (5b)] carried out the highly convenient base-free Michael addition of the activated C,H compounds across ,,,-unsaturated carbonyl compounds in air at room temperature. The complexes 1b,5b were synthesized by the direct reaction of the respective imidazolium chloride salt with NiCl2·6H2O in CH3CN in the presence of K2CO3 as a base. The exceptional stability of 1b,5b has been attributed to the deeply buried nickel,NHC ,-bonding molecular orbitals as evidenced from the density functional theory (DFT) studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Palladium-Catalyzed Desulfitative Mizoroki,Heck Couplings of Sulfonyl Chlorides with Mono- and Disubstituted Olefins: Rhodium-Catalyzed Desulfitative Heck-Type Reactions under Phosphine- and Base-Free Conditions.

CHEMINFORM, Issue 14 2006
Srinivas Reddy Dubbaka
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

Palladium-Catalyzed Desulfitative Mizoroki,Heck Couplings of Sulfonyl Chlorides with Mono- and Disubstituted Olefins: Rhodium-Catalyzed Desulfitative Heck-Type Reactions under Phosphine- and Base-Free Conditions

CHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2005
Srinivas Reddy Dubbaka
Abstract New conditions have been found for the desulfitative Mizoroki,Heck arylation and trifluoromethylation of mono- and disubustituted olefins with arenesulfonyl and trifluoromethanesulfonyl chlorides. Thus (E)-1,2-disubstituted alkenes with high stereoselectivity and 1,1,2-disubstituted alkenes with 12:1 to 21:1 E/Z steroselectivity can be obtained. Herrmann's palladacycle at 0.1 mol,% is sufficient to catalyze these reactions, for which electron-rich or electron-poor sulfonyl chlorides and alkenes are suitable. If phosphine- and base-free conditions are required, 1 mol,% [RhCl(C2H4)2] catalyzes the desulfitative cross-coupling reactions. Contrary to results reported for [RuCl2(PPh3)2]-catalyzed coupling reactions with sulfonyl chlorides, the palladium and rhodium desulfitative Mizoroki,Heck coupling reactions are not inhibited by radical scavenging agents. Possible sulfones arising from the sulfonylation of alkenes at 60,°C are not desulfitated at higher temperatures in the presence of the Pd or Rh catalysts. De nouvelles conditions sont rapporteés pour les couplages désulfitants du type Mizoroki,Heck des chlorures d'arènesulfonyles et trifluorométhanesulfonyle avec des oléfines mono- et disubstitueés. La méthode permet la synthèse de (E)-alcènes 1,2-disubstitués avec haute stéréosélectivité et d'alkènes 1,1,2-trisubstitués avec des stéréosélectivités E/Z variant de 12:1 à 21:1. La palladacycle de Herrmann à 0.1 mol% est suffisant pour catalyser ces reactions qui peuvent engager des chlorures de sulfonyles et des alcènes soit riches ou pauvres en électron. Si des conditions sans phosphine et sans base sont requises, 1 mol,% de [RhCl(C2H4)2] est un excellent catalyseur pour ces couplages désulfitants. Contrairement à ce qui est rapporté pour des réactions analogues catalysées par [RuCl2(PPh3)2] et qui impliquent des intermédiaires radicalaires, les couplages du type Mizoroki,Heck désulfitants catalysés par des complexes de palladium ou de rhodium ne sont pas inhibés par des pièges à radicaux. De plus, les sulfones qui peuvent se former par sulfonylation des alcènes (60,oC) ne sont pas désulfitées à plus haute température en présence des catalyseurs au Pd ou au Rh. [source]

Nickel Complexes of N/O -Functionalized N-Heterocyclic Carbenes as Precatalysts for Michael Reactions in Air at Room Temperature Under the Much Preferred Base-Free Conditions

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2009
Sriparna Ray
Abstract A series of several new nickel precatalysts supported overN/O -functionalized N-heterocyclic carbenes (NHC) for the Michael reactions of ,-dicarbonyl, ,-keto ester, ,-diester, and ,-cyano ester compounds with ,,,-unsaturated carbonyl compounds in air at ambient temperature under the much preferred base-free conditions are reported. Specifically, the nickel complexes, [1-(R1 -aminocarbonylmethyl)-3-R2 -imidazol-2-ylidene]2Ni [R1 = 2-C6H4(OMe); R2 = Me (1b), iPr (2b), CH2Ph (3b) and R1 = 2-CH2C4H3O; R2 = Me (4b), CH2Ph (5b)] carried out the highly convenient base-free Michael addition of the activated C,H compounds across ,,,-unsaturated carbonyl compounds in air at room temperature. The complexes 1b,5b were synthesized by the direct reaction of the respective imidazolium chloride salt with NiCl2·6H2O in CH3CN in the presence of K2CO3 as a base. The exceptional stability of 1b,5b has been attributed to the deeply buried nickel,NHC ,-bonding molecular orbitals as evidenced from the density functional theory (DFT) studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

An Efficient N -Arylation of Heterocycles with Aryl-, Heteroaryl-, and Vinylboronic Acids Catalyzed by Copper Fluorapatite

HELVETICA CHIMICA ACTA, Issue 5 2010
Lakshmi Kantam, Mannepalli
Abstract N -Arylation of N-containing heterocycles, such as pyrazoles, imidazoles, and benzimidazoles with aryl-, heteroaryl-, and vinylboronic acids was efficiently carried out by copper fluorapatite (CuFAP) catalyst in MeOH at room temperature under base-free conditions. The N- arylated heterocycles were isolated in good-to-excellent yields. [source]

Synthesis of Fused and Linked Bicyclic Nitrogen Heterocycles by Palladium-Catalyzed Domino Cyclization of Propargyl Bromides

CHEMISTRY - A EUROPEAN JOURNAL, Issue 28 2010
Akinori Okano Dr.
Abstract The palladium(0)-catalyzed direct construction of bicyclic heterocycles is described. Treatment of propargyl bromides that have nucleophilic functional groups connected by two or three carbon atoms with catalytic [Pd(PPh3)4] affords bis-cyclization products in good yields. The desired bicyclic heterocycles can be obtained selectively when using substrates with appropriate nucleophilic groups. We also describe the reaction of a 2-alkynylazetidine derivative with a catalytic amount of [Pd(PPh3)4] under base-free conditions, which affords the same fused heterocycles as the corresponding propargyl bromides. [source]

Palladium-Catalyzed Desulfitative Mizoroki,Heck Couplings of Sulfonyl Chlorides with Mono- and Disubstituted Olefins: Rhodium-Catalyzed Desulfitative Heck-Type Reactions under Phosphine- and Base-Free Conditions

CHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2005
Srinivas Reddy Dubbaka
Abstract New conditions have been found for the desulfitative Mizoroki,Heck arylation and trifluoromethylation of mono- and disubustituted olefins with arenesulfonyl and trifluoromethanesulfonyl chlorides. Thus (E)-1,2-disubstituted alkenes with high stereoselectivity and 1,1,2-disubstituted alkenes with 12:1 to 21:1 E/Z steroselectivity can be obtained. Herrmann's palladacycle at 0.1 mol,% is sufficient to catalyze these reactions, for which electron-rich or electron-poor sulfonyl chlorides and alkenes are suitable. If phosphine- and base-free conditions are required, 1 mol,% [RhCl(C2H4)2] catalyzes the desulfitative cross-coupling reactions. Contrary to results reported for [RuCl2(PPh3)2]-catalyzed coupling reactions with sulfonyl chlorides, the palladium and rhodium desulfitative Mizoroki,Heck coupling reactions are not inhibited by radical scavenging agents. Possible sulfones arising from the sulfonylation of alkenes at 60,°C are not desulfitated at higher temperatures in the presence of the Pd or Rh catalysts. De nouvelles conditions sont rapporteés pour les couplages désulfitants du type Mizoroki,Heck des chlorures d'arènesulfonyles et trifluorométhanesulfonyle avec des oléfines mono- et disubstitueés. La méthode permet la synthèse de (E)-alcènes 1,2-disubstitués avec haute stéréosélectivité et d'alkènes 1,1,2-trisubstitués avec des stéréosélectivités E/Z variant de 12:1 à 21:1. La palladacycle de Herrmann à 0.1 mol% est suffisant pour catalyser ces reactions qui peuvent engager des chlorures de sulfonyles et des alcènes soit riches ou pauvres en électron. Si des conditions sans phosphine et sans base sont requises, 1 mol,% de [RhCl(C2H4)2] est un excellent catalyseur pour ces couplages désulfitants. Contrairement à ce qui est rapporté pour des réactions analogues catalysées par [RuCl2(PPh3)2] et qui impliquent des intermédiaires radicalaires, les couplages du type Mizoroki,Heck désulfitants catalysés par des complexes de palladium ou de rhodium ne sont pas inhibés par des pièges à radicaux. De plus, les sulfones qui peuvent se former par sulfonylation des alcènes (60,oC) ne sont pas désulfitées à plus haute température en présence des catalyseurs au Pd ou au Rh. [source]