- Atom Economic Ruthenium-Catalyzed Synthesis of Bulky β-Oxo Esters
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Ruthenium complexes with the formulae Ru(CO)2(PR3)2(O2CPh)2 [6a-h; R=n-Bu, p-MeO-C6H4, p-Me-C6H4, Ph, p-Cl-C6H4, m-Cl-C6H4, p-CF3-C6H4, m,m′-(CF3)2C6H3] were prepared by treatment of triruthenium dodecacarbonyl [Ru3(CO)12] with the respective phosphine and benzoic acid or by the conversion of Ru(CO)3(PR3)2 (8e-h) with benzoic acid. During the preparation of 8, ruthenium hydride complexes of type Ru(CO)(PR3)3(H)2 (9g, h) could be isolated as side products. The molecular structures of the newly synthesized complexes 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 β-oxo esters. The catalyst screening revealed a considerably influence of the phosphine′s electronic nature on the resulting activities. The best performances were obtained with complexes 6g and 6h, featuring electron-withdrawing phosphine ligands. Additionally, catalyst 6g is very active in the conversion of sterically demanding substrates, leading to a broad substrate scope. The catalytic preparation of simple as well as challenging substrates succeeds with catalyst 6g in yields that often exceed those of established literature systems. Furthermore, the reactions can be carried out with catalyst loadings down to 0.1mol% and reaction temperatures down to 50 C.
- Jeschke, Janine,Korb, Marcus,Rüffer, Tobias,G?bler, Christian,Lang, Heinrich
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supporting information
p. 4069 - 4081
(2016/01/25)
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- Ruthenium(IV)-catalyzed markovnikov addition of carboxylic acids to terminal alkynes in aqueous medium
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The dimeric bis(allyl)ruthenium(IV) complex [{RuCl(μ-Cl)( η3:η3-C10H16)}2] (C10H16 = 2,7-dimethylocta-2,6-diene-1,8-diyl) (5) and several mononuclear species trans-[RuCl2(η3: η3-C10H16)(L)] (L = two-electron-donor ligand) (6) derived from 5 have been checked as catalysts for the addition of carboxylic acids onto terminal alkynes using water as a green reaction medium. The best results in terms of activity and regioselectivity were obtained with the mononuclear derivative trans-[RuCl2(η3: η3-C10H16)(PPh3)] (6a), which was able to promote the selective Markovnikov addition of both aromatic and aliphatic carboxylic acids to a large variety of terminal alkynes, enynes, and diynes as well as propargylic alcohols. In this way, a wide number of enol esters and β-oxo esters could be synthesized in moderate to good yields under mild conditions (60 °C) in an aqueous medium.
- Cadierno, Victorio,Francos, Javier,Gimeno, Jose
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experimental part
p. 852 - 862
(2011/04/15)
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- Ruthenium-catalyzed synthesis of β-oxo esters in aqueous medium: Scope and limitations
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The ability of the hydrosoluble ruthenium(ii) complexes [RuCl 2(η6-arene)(PTA)] 3a-d, [RuCl2(η 6-arene)(PTA-Bn)] 4a-d, [RuCl2(η6-arene) (DAPTA)] 5a-d, [RuCl2(η6-arene)(TPPMS)] 6a-d (arene = C6H6, p-cymene, 1,3,5-C6H3Me 3, C6Me6) to promote the atom-economic formation of β-oxo esters, by addition of carboxylic acids to terminal propargylic alcohols in water has been explored. Scope, limitations and catalyst recycling have been evaluated using the most active catalyst [RuCl 2(η6-C6H6)(TPPMS)], 6a.
- Cadierno, Victorio,Francos, Javier,Gimeno, Jose
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experimental part
p. 135 - 143
(2010/05/18)
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