Imidazolsynthesen, 8. Mitt.: N‐Substituierte Imidazole nach Weidenhagen

Stoeck, V.; Schunack, Walter

doi:10.1002/ardp.19763090514

Cited by 25 publications

(8 citation statements)

References 10 publications

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“…[18] In addition,t hey are intermediates in the synthesis of furanones [19] and imidazoles. [20] In comparison to other known synthetic methodologies for the preparation of b-oxo esters, e.g.,t he two-steph ydration/esterification of propargylic alcohols, [21] the carboxylation of a-halo ketones, [18a] the copper-catalyzedi nsertion of a-diazok etones into the O À Hb ondo fc arboxylic acids, [22] the Wacker oxidation of allyl carboxylates [23] or the oxidation of ketones with metal acetate complexes, [24] the direct ruthenium-catalyzed addition is the most straightforward anda tom-economical route.M oreover, the reaction conditions are relatively mild (60 to 120 8 8C) and the substrates are simple andc ommercially available. [25] Thep roposedm echanism for the ruthenium-catalyzed formation of b-oxo esters starts with the nucleophilic attack of the carboxylica cid to the h 2 -alkyne ruthenium complex A giving Markovnikov addition.…”

Section: Introductionmentioning

confidence: 99%

Atom Economic Ruthenium‐Catalyzed Synthesis of Bulky β‐Oxo Esters

et al. 2015

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Ruthenium complexes with the formulae Ru(CO) 2 (PR 3 ) 2 (O 2 CPh) 2 [6a-h;R = n-Bu, p-MeO-C 6 H 4 , p-Me-C 6 H 4 ,P h, p-Cl-C 6 H 4 , m-Cl-C 6 H 4 , p-CF 3 -C 6 H 4 , m,m'-(CF 3 ) 2 C 6 H 3 ]w ere prepared by treatment of triruthenium dodecacarbonyl [Ru 3 (CO) 12 ]w ith the respective phosphine and benzoic acid or by the conversion of Ru(CO) 3 (PR 3 ) 2 (8e-h)w ith benzoic acid. During the preparation of 8,r uthenium hydride complexes of type Ru(CO)(PR 3 ) 3 (H) 2 (9g, h)c ould be isolated as side products. Them olecular structures of the newly synthesizedc omplexes in the solid state are discussed. Compounds 6a-h were found to be highly effective catalysts in the addition of carboxylic acids to propargylic alcohols to give valuable b-oxo esters.T he catalyst screening revealed ac onsiderably influence of the phosphine'se lectronicn ature on the resulting activities. Theb est performances were obtained with complexes 6g and 6h,f eaturing electron-withdrawing phosphine ligands.A dditionally,c atalyst 6g is very active in the conversion of sterically demanding substrates,l eading to ab road substrate scope.T he catalytic preparation of simple as wella sc hallenging substrates succeeds with catalyst 6g in yields that often exceed those of established literature systems.F urthermore,t he reactions can be carriedo ut with catalyst loadings down to 0.1 mol% andr eactiont emperatures down to 50 8 8C.

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Section: Introductionmentioning

confidence: 99%

Atom Economic Ruthenium‐Catalyzed Synthesis of Bulky β‐Oxo Esters

et al. 2015

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“…[1][2][3][4] Furthermore, β-oxopropyl esters are basic intermediates in the synthesis of α-hydroxy ketones, [5] furanones, [6,7] imidazoles, [8] and amides and peptides. [1][2][3][4] Furthermore, β-oxopropyl esters are basic intermediates in the synthesis of α-hydroxy ketones, [5] furanones, [6,7] imidazoles, [8] and amides and peptides.…”

Section: Introductionmentioning

confidence: 99%

Ruthenium Carboxylate Complexes as Efficient Catalysts for the Addition of Carboxylic Acids to Propargylic Alcohols

et al. 2015

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Ruthenium complexes [Ru(CO) 2 (PPh 3 ) 2 (O 2 CR) 2 ] -3a (R = CH 2 OCH 3 ), 3b (R = iPr), 3c (R = tBu), 3d (R = 2-c C 4 H 3 O), and 3e (R = Ph) -were synthesized by treatment of Ru(CO) 3 -(PPh 3 ) 2 with the corresponding carboxylic acids. The molecular structures of the newly synthesized complexes in the solid state are discussed. Compounds 3a-e were successfully applied as catalysts in the addition of carboxylic acids to propargylic alcohols to give the corresponding β-oxo esters in good to excellent yields even in air. The different carboxylate ligands do not have an influence on the productivities, because the carboxylates exchange rapidly under the applied [a]2939 reaction conditions, as was confirmed by 31 P{ 1 H} NMR spectroscopic studies. The addition of catalytic amounts of Na 2 CO 3 resulted in an increase in β-oxo ester formation. The reaction is tolerant to the use of versatile functional groups on the propargylic alcohols and carboxylic acids, revealing a broad substrate generality. In contrast to most other known catalytic systems, even sterically hindered substrates, including 2,4,6-trimethylbenzoic acid, 1,1-diphenylprop-2-yn-1-ol, or the biologically active steroid ethisterone, were successfully converted.

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“…10 Solid and Lewis acid catalysts have been of great interest in organic synthesis. 11 There are many methods for the synthesis of polysubstituted imidazoles by employing of Lewis acids 12 such as condensation of diones, aldehydes, primary amines and ammonia in the presence of various acid catalysts, [13][14][15] N-alkylation of trisubstituted imidazoles, 16 condensation of benzil or * For correspondence benzoin acetate with aldehydes, primary amines and ammonia in the presence of copper acetate, 17,18 condensation of o-diamines with aldehydes and in the presence of tetrabutylammonium fluoride (TBAF), 19 etc. The first method is the most well-known and classical method.…”

Section: Introductionmentioning

confidence: 99%

New and rapid access to synthesis of novel polysubstituted imidazoles using antimony trichloride and stannous chloride dihydrate as effective and reusable catalysts

et al. 2013

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In this work, new, efficient and environmentally adapted synthesis of polysubstituted imidazoles in one-pot is repoted. The multicomponent reaction of various aldehydes, benzil, aliphatic and aromatic primary amines and ammonium acetate under solvent-free condition is explained. The highly efficient role of antimony trichloride and stannous chloride dihydrate as catalyst in this synthesis was shown and their effects on the reaction process were studied. By this advantage, several polysubstituted imidazoles as pharmaceutical important molecules can be prepared in high yield and high purity. This method is a very easy and rapid for the synthesis of imidazole derivatives.

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Imidazolsynthesen, 8. Mitt.: N‐Substituierte Imidazole nach Weidenhagen

Abstract: Die Weidenhagen‐Synthese N‐unsubstituierter Imidazole aus α‐substituierten Carbonylverbindungen 1, Aldehyden 3, wäßrigem Ammoniak (4) und Kupfer(II)‐salzen als Oxidationsmittel ist in Gegenwart primärer Amine 5 auch zur Darstellung N‐substituierter Imidazole 6 geeignet.

Cited by 25 publications

References 10 publications

Atom Economic Ruthenium‐Catalyzed Synthesis of Bulky β‐Oxo Esters

Atom Economic Ruthenium‐Catalyzed Synthesis of Bulky β‐Oxo Esters

Ruthenium Carboxylate Complexes as Efficient Catalysts for the Addition of Carboxylic Acids to Propargylic Alcohols

New and rapid access to synthesis of novel polysubstituted imidazoles using antimony trichloride and stannous chloride dihydrate as effective and reusable catalysts

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