- Engineering Catalysts for Selective Ester Hydrogenation
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The development of efficient catalysts and processes for synthesizing functionalized (olefinic and/or chiral) primary alcohols and fluoral hemiacetals is currently needed. These are valuable building blocks for pharmaceuticals, agrochemicals, perfumes, and so forth. From an economic standpoint, bench-stable Takasago Int. Corp.'s Ru-PNP, more commonly known as Ru-MACHO, and Gusev's Ru-SNS complexes are arguably the most appealing molecular catalysts to access primary alcohols from esters and H2 (Waser, M. et al. Org. Proc. Res. Dev. 2018, 22, 862). This work introduces economically competitive Ru-SNP(O)z complexes (z = 0, 1), which combine key structural elements of both of these catalysts. In particular, the incorporation of SNP heteroatoms into the ligand skeleton was found to be crucial for the design of a more product-selective catalyst in the synthesis of fluoral hemiacetals under kinetically controlled conditions. Based on experimental observations and computational analysis, this paper further extends the current state-of-the-art understanding of the accelerative role of KO-t-C4H9 in ester hydrogenation. It attempts to explain why a maximum turnover is seen to occur starting at 25 mol % base, in contrast to only 10 mol % with ketones as substrates.
- Dub, Pavel A.,Batrice, Rami J.,Gordon, John C.,Scott, Brian L.,Minko, Yury,Schmidt, Jurgen G.,Williams, Robert F.
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p. 415 - 442
(2020/03/04)
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- SYNTHESIS OF FLUORO HEMIACETALS VIA TRANSITION METAL-CATALYZED FLUORO ESTER AND CARBOXAMIDE HYDROGENATION
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This application is directed to use of transition metal-ligand complexes to hydrogenate fluorinated esters and carboxamides into fluorinated hemiacetals. Methods for synthesis of certain ligands are also provided.
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Paragraph 0237-0238; 0259-0260
(2020/11/24)
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- Alpha,Alpha-Difluoroacetaldehyde Production Method
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A production method of α,α-difluoroacetaldehyde according to the present invention includes reaction of an α,α-difluoroacetic acid ester with hydrogen gas (H2) in the presence of a ruthenium catalyst. It is possible to selectively obtain α,α-difluoroacetaldehyde as a partially reduced product of the hydrogenation reaction by the adoption of specific reaction conditions (in particular, reaction solvent and reaction temperature). This hydrogenation process can be alternative to the industrially unpractical hydride reduction process.
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Paragraph 0082; 0083; 0084
(2016/01/30)
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- Practical selective hydrogenation of α-fluorinated esters with bifunctional pincer-type ruthenium(II) catalysts leading to fluorinated alcohols or fluoral hemiacetals
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Selective hydrogenation of fluorinated esters with pincer-type bifunctional catalysts RuHCl(CO)(dpa) 1a, trans-RuH2(CO)(dpa) 1b, and trans-RuCl2(CO)(dpa) 1c under mild conditions proceeds rapidly to give the corresponding fluorinated alcohols or hemiacetals in good to excellent yields. Under the optimized conditions, the hydrogenation of chiral (R)-2-fluoropropionate proceeds smoothly to give the corresponding chiral alcohol without any serious decrease of the ee value.
- Otsuka, Takashi,Ishii, Akihiro,Dub, Pavel A.,Ikariya, Takao
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supporting information
p. 9600 - 9603
(2013/07/26)
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