- Binuclear Pd(I)-Pd(I) Catalysis Assisted by Iodide Ligands for Selective Hydroformylation of Alkenes and Alkynes
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Since its discovery in 1938, hydroformylation has been thoroughly investigated and broadly applied in industry (>107 metric ton yearly). However, the ability to precisely control its regioselectivity with well-established Rh- or Co-catalysts has thus far proven elusive, thereby limiting access to many synthetically valuable aldehydes. Pd-catalysts represent an appealing alternative, yet their use remains sparse due to undesired side-processes. Here, we report a highly selective and exceptionally active catalyst system that is driven by a novel activation strategy and features a unique Pd(I)-Pd(I) mechanism, involving an iodide-assisted binuclear step to release the product. This method enables β-selective hydroformylation of a large range of alkenes and alkynes, including sensitive starting materials. Its utility is demonstrated in the synthesis of antiobesity drug Rimonabant and anti-HIV agent PNU-32945. In a broader context, the new mechanistic understanding enables the development of other carbonylation reactions of high importance to chemical industry.
- Zhang, Yang,Torker, Sebastian,Sigrist, Michel,Bregovi?, Nikola,Dydio, Pawe?
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supporting information
p. 18251 - 18265
(2020/11/02)
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- Selective hydroformylation of alkyl acrylates using [2,2′-bis(dipyrrolylphosphinooxy)-1,1′-(±)-binaphthyl]/Rh catalyst: reversal of regioselectivity
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The rhodium-catalyzed hydroformylation of alkyl acrylates with different P-N diphosphine ligands is investigated here. Under mild conditions (syngas pressure: 2 MPa, 20 °C), 2,2′-bis(dipyrrolylphosphinooxy)-1,1′-(±)-binaphthyl (L1) rhodium catalyst could give good conversion of ethyl acrylate (82.9%) in 12 h and exclusive branched aldehyde selectivity of >99.0%. More importantly, on elevating the temperature to 90 °C, this Rh system could preferentially afford the linear aldehyde with 96.1% regioselectivity, and the TOF could reach up to 9000 h?1. Deuterioformylation was conducted to explore the mechanism of regioselectivity reversal, and the results established that the reversible rhodium hydride addition to form the Rh-alkyl species might play a vital role in this reversal. The β-hydride elimination of branched Rh-alkyl species was comparatively stronger than that of linear ones under increased temperature, probably because L1 could cause comparatively larger steric repulsion in branched Rh-alkyl species under high temperature, due to its bulky and rigid binaphthyl backbone characteristics. In turn, the linear Rh-alkyl species progress to linear aldehyde was facilitated.
- Shu, Xiao,Liang, Haoran,Wu, Qianhui,Zhou, Fanding,Zheng, Xueli,Fu, Haiyan,Xu, Bin,Li, Ruixiang,Zhang, Chunchun,Chen, Hua
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p. 14816 - 14823
(2017/03/16)
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- Catalysis by water-soluble organometallic complexes in water-in-densified fluid microemulsions
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A microemulsion containing water, a densified fluid, a surfactant, and an organometallic catalyst is used to catalyze chemical reactions. The organometallic catalyst preferably has substantial solubility in the water phase of the microemulsion. Separation of reaction products from the microemulsion is facilitated by removal of the densified fluid.
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- Hydroformylation with unmodified rhodium catalysts in supercritical carbon dioxide
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The present invention relates to processes for the preparation of oxo products by the hydroformylation of substrates having C═C double bonds using unmodified rhodium catalysts in a reaction mixture essentially consisting of the substrates, the catalyst and carbon dioxide in a supercritical state (scCO2). In particular, the invention relates to such processes for the preparation of products which contain substantial proportions of branched i-oxo products. Further, the invention relates to such processes for the hydroformylation of substrates which do not correspond to the general formula CnH2n. The invention further relates to such processes in which the separation of product and catalyst is effected using the special solvent properties of scCO2.
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Page column 5-7
(2008/06/13)
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- Evidence for Ketene Intermediates in the Reactions of 2-Oxobutanedioic Acid Diesters with Alcohols and Water
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The reactions of diethyl ester (1a) and dimethyl ester (1b) of 3-methyl-2-oxobutanedioic acid with excess ethanol, methanol, or water in a sealed tube at approximately 125 deg C were studied.With methanol, 1a yielded mainly 3-methyl-2-oxobutanedioic acid 1-ethyl 4-methyl diester, 2a; with ethanol, 1b yielded mainly the 4-ethyl 1-methyl diester, 2b, while reaction of 1a with water yielded carbon dioxide, 2-oxobutanoic acid ethyl ester, 6, and 2-methyl-3-oxopropanoic acid ethyl ester, 7.These results suggested that the ketene intermediates 3-methyl-2,4-dioxo-3-butenoic acid ethyl or methyl ester, 4a and 4b, respectively, are implicated.The similarity of these reactions to those exhibited by ethyl acetoacetate, such as alkoxy group exchange, and formation of dehydroacetic acid, now thought to proceed by way of acetyl ketene, was demonstrated.
- Emerson, David W.,Titus, Richard L.,Gonzalez, Rowena M.
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p. 3572 - 3576
(2007/10/02)
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- High catalytic activity of - for hydroformylation of olefins
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Comparison of the catalytic activity of - with those of the known catalyst systems (- and Ru3(CO)12) has revealed that - is an active catalyst for hydroformylation of 1-pentene, styrene, and ethyl acrylate. - partly reduces the aldehydes initially formed into their corresponding alcohols.In the reaction of ethyl acrylate catalyzed by - or -, significant amounts of carbonylative dimers (diethyl 2-formyl-2-methylglutarate and 4-ethoxycarbonyl-4-methyl-δ-valerolactone) were also formed.
- Hayashi, Teruyuki,Gu, Zheng Hui,Sakakura, Toshiyasu,Tanaka, Masato
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p. 373 - 378
(2007/10/02)
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