Enantioselective Monofluoromethylation Reaction

Mizuta, Satoshi; Shibata, Naoyuki; Goto, Yasumasa; Furukawa, T.; Nakamura, Shinji; Toru, Takeshi

doi:10.1055/s-2007-968629

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2007

DOI: 10.1055/s-2007-968629

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Enantioselective Monofluoromethylation Reaction

Satoshi Mizuta¹,

Naoyuki Shibata²,

Yasumasa Goto³

et al.

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“…[3] As part of our ongoing studies in medicinal fluorine chemistry, [4] we describe herein the highly enantioselective synthesis of oxindoles 3 with two contiguous asymmetric quaternary carbon atoms, including a tertiary a-trifluoromethyl alcohol center, [5] by an asymmetric direct aldol-type condensation of oxindoles with ethyl 3,3,3-trifluoropyruvate (2) under the catalysis of cinchona alkaloids.…”

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Cinchona‐Alkaloid‐Catalyzed Enantioselective Direct Aldol‐Type Reaction of Oxindoles with Ethyl Trifluoropyruvate

Ogawa¹,

Shibata²,

Inagaki³

et al. 2007

Angew Chem Int Ed

204

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Heterocycles that contain a trifluoromethyl group are important compounds in agricultural and medicinal chemistry. Therefore, the development of a simple and flexible method for the generation of trifluoromethylated heterocyclic systems has received much attention.[1] We believed that the incorporation of a tertiary a-trifluoromethyl alcohol stereocenter (CF 3 C*(OH)R 1 R 2 ) into heterocycles could provide novel drug candidates with unusual biological activities as a result of the unique properties of the tertiary a-trifluoromethyl alcohol functionality.[2] We first became interested in the development of general methods for the synthesis of oxindoles with a tertiary a-trifluoromethyl alcohol moiety in a chiral environment. Oxindoles with a quaternary stereogenic center, especially spirooxindoles, are of potential medicinal interest owing to the unique biological activities of natural products and man-made compounds that contain such systems.[3] As part of our ongoing studies in medicinal fluorine chemistry, [4] we describe herein the highly enantioselective synthesis of oxindoles 3 with two contiguous asymmetric quaternary carbon atoms, including a tertiary a-trifluoromethyl alcohol center, [5] by an asymmetric direct aldol-type condensation of oxindoles with ethyl 3,3,3-trifluoropyruvate (2) under the catalysis of cinchona alkaloids.[6] The two enantiomeric products (S,S)-3 and (R,R)-3 are accessible selectively in high yields with up to 99 % ee with pseudoenantiomeric cinchona alkaloids (Scheme 1).Trifluoropyruvate is one of the most versatile building blocks for the synthesis of chiral trifluoromethylated compounds. Examples of enantioselective nucleophilic addition to trifluoropyruvate in the Friedel-Crafts reaction, the aldol reaction, the Henry reaction, and the carbonyl-ene reaction under the catalysis of chiral Lewis acids, cinchona alkaloids, or proline derivatives have been reported. [7] However, there is no information available on the use of oxindoles as nucleophiles in the corresponding asymmetric addition reactions. We first attempted the enantioselective aldol-type reaction of 3-methyl-2-oxindole (1 a; R 1 = Me, R 2 = H; Scheme 1) with 2 in the presence of cinchonidine as a catalyst.Cinchonidine was found to be an effective catalyst for the enantioselective Friedel-Crafts reaction of indoles reported by Prakash and co-workers; [7e] however, in the direct aldoltype reaction of 1 a with 2, the adduct 3 a was obtained in 67 % yield with poor diastereoselectivity and 50 % ee (Table 1, entry 1). At best only a slight improvement in the diastereomeric ratio and enantioselectivity was observed with other Scheme 1. Aldol-type reaction of oxindoles 1 with ethyl trifluoropyruvate (2) under the catalysis of cinchona alkaloids.

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mentioning

confidence: 99%

Cinchona‐Alkaloid‐Catalyzed Enantioselective Direct Aldol‐Type Reaction of Oxindoles with Ethyl Trifluoropyruvate

Ogawa¹,

Shibata²,

Inagaki³

et al. 2007

Angew Chem Int Ed

204

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Rare‐Earth Metal Allyl and Hydrido Complexes Supported by an (NNNN)‐Type Macrocyclic Ligand: Synthesis, Structure, and Reactivity toward Biomass‐Derived Furanics

Abinet

Martin

Standfuss

et al. 2011

Chemistry A European J

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The preparation and characterization of a series of neutral rare-earth metal complexes [Ln(Me(3)TACD)(η(3)-C(3)H(5))(2)] (Ln=Y, La, Ce, Pr, Nd, Sm) supported by the 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane anion (Me(3)TACD(-)) are reported. Upon treatment of the neutral allyl complexes [Ln(Me(3)TACD)(η(3)-C(3)H(5))(2)] with Brønsted acids, monocationic allyl complexes [Ln(Me(3)TACD)(η(3)-C(3)H(5))(thf)(2)][B(C(6)X(5))(4)] (Ln=La, Ce, Nd, X=H, F) were isolated and characterized. Hydrogenolysis gave the hydride complexes [Ln(Me(3)TACD)H(2)](n) (Ln=Y, n=3; La, n=4; Sm). X-ray crystallography showed the lanthanum hydride to be tetranuclear. Reactivity studies of [Ln(Me(3)TACD)R(2)](n) (R=η(3)-C(3)H(5), n=0; R=H, n=3,4) towards furan derivatives includes hydrosilylation and deoxygenation under ring-opening conditions.

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Enantioselective Monofluoromethylation Reaction

Cited by 2 publications

References 0 publications

Cinchona‐Alkaloid‐Catalyzed Enantioselective Direct Aldol‐Type Reaction of Oxindoles with Ethyl Trifluoropyruvate

Cinchona‐Alkaloid‐Catalyzed Enantioselective Direct Aldol‐Type Reaction of Oxindoles with Ethyl Trifluoropyruvate

Rare‐Earth Metal Allyl and Hydrido Complexes Supported by an (NNNN)‐Type Macrocyclic Ligand: Synthesis, Structure, and Reactivity toward Biomass‐Derived Furanics

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