Enantioselective synthesis of 2,2-difluoro-3-hydroxycarboxylates by rhodium-catalyzed hydrogenation

Kuroki, Yoshichika; Asada, Daisuke; Iseki, Katsuhiko

doi:10.1016/s0040-4039(00)01744-5

Cited by 44 publications

(15 citation statements)

References 22 publications

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“…[4] High optical purities were observed only in the hydrogenations of 2,2-difluoro-3-oxocarboxylates. [5] In spite of the well known advantages of the heterogeneous catalysts, i.e., easy handling, separation and reuse of the catalyst, such catalytic systems have not been tested yet in the hydrogenation of a-monofluoro ketones. Thus, we have decided to investigate the hydrogenation of racemic ethyl 2-fluoroacetoacetate (1), using the Cinchona alkaloid-modified Pt catalyst which, as mentioned Scheme 1.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Kinetic Resolution over Cinchona‐Modified Platinum Catalyst: Hydrogenation of Racemic Ethyl 2‐Fluoroacetoacetate

2006

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Abstract:The enantioselective hydrogenation over a Cinchona alkaloid-modified supported platinum catalyst and parallel spontaneous racemization under the reaction conditions of the unreacted enantiomer of ethyl 2-fluoroacetoacetate are described. Using the appropriate reaction conditions an 82% enantiomeric excess in favor of the (2S,3R)-ethyl 2-fluoro-3-hydroxybutanoate and a 99/1 threo/erythro ratio were obtained. This novel method for producing optically enriched a-fluoro-b-hydroxy esters is the first example of dynamic kinetic resolution of a chirally labile racemic fluorinated compound over a modified heterogeneous metal catalyst carried out without using supplementary additives except the chiral modifier. The hydrogenation described here shows that the activation of the keto group of acetoacetates by one fluorine atom in the a position is also sufficient for obtaining high enantiomeric excess in the Orito reaction.

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Section: Introductionmentioning

confidence: 99%

Dynamic Kinetic Resolution over Cinchona‐Modified Platinum Catalyst: Hydrogenation of Racemic Ethyl 2‐Fluoroacetoacetate

2006

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“…A viable route to chiral a,a,a-trifluoromethyl alcohols is the enantioselective hydrogenation of trifluoromethyl ketones. Some chiral transition metal catalysts afforded excellent yields and ees up to 98% [24,25]. The efficiency of the platinum-cinchona system in this reaction class is extremely substrate specific: at best 92-96% ee was achieved under mild reaction conditions [26,27] but for many substrates the enantioselectivities were medium to low or no reaction occurred at all [28][29][30][31].…”

Section: Introductionmentioning

confidence: 99%

An efficient synthetic chiral modifier for platinum

et al. 2005

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A new chiral modifier pantoyl-naphthylethylamine (PNEA) was synthesized by reductive alkylation of 1-(1-naphthyl)ethylamine with ketopantolactone. Platinum-on-alumina modified by PNEA afforded 93% ee and 100% chemoselectivity in the hydrogenation of the activated carbonyl group of 1,1,1-trifluoro-2,4-pentanedione. Reductive heat treatment and ultrasonication of the catalyst, and the use of chlorinated solvents under mild conditions (10 bar, 10°C) enhanced the enantioselectivity. This is the first case in heterogeneous catalysis that a synthetic modifier gives more than 90% ee, better than the commonly used modifier of natural origin (cinchonidine or O-methyl-cinchonidine).

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“…Some soluble chiral transition metal catalysts afforded excellent ees (up to 98% [33,34]). The efficiency of cinchonidine (CD)-modified Pt is highly substrate specific.…”

Section: Introductionmentioning

confidence: 99%

Chemo and enantioselective hydrogenation of fluorinated ketones on platinum modified with (R)-1-(1-naphthyl)ethylamine derivatives

Diezi¹,

Hess²,

Orglmeister³

et al. 2005

Journal of Molecular Catalysis A: Chemical

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Enantioselective synthesis of 2,2-difluoro-3-hydroxycarboxylates by rhodium-catalyzed hydrogenation

Cited by 44 publications

References 22 publications

Dynamic Kinetic Resolution over Cinchona‐Modified Platinum Catalyst: Hydrogenation of Racemic Ethyl 2‐Fluoroacetoacetate

Dynamic Kinetic Resolution over Cinchona‐Modified Platinum Catalyst: Hydrogenation of Racemic Ethyl 2‐Fluoroacetoacetate

An efficient synthetic chiral modifier for platinum

Chemo and enantioselective hydrogenation of fluorinated ketones on platinum modified with (R)-1-(1-naphthyl)ethylamine derivatives

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