36 research outputs found

    Asymmetric Synthesis of Triarylmethanes by Rhodium-Catalyzed Enantioselective Arylation of Diarylmethylamines with Arylboroxines

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    The reaction of racemic diarylmethylamines, (Ar<sup>1</sup>Ar<sup>2</sup>CHNR<sub>2</sub>), where Ar<sup>1</sup> is substituted with a 2-hydroxy group, with arylboroxines (Ar<sup>3</sup>BO)<sub>3</sub> in the presence of a chiral diene-rhodium catalyst gave high yields of chiral triarylmethanes (Ar<sup>1</sup>Ar<sup>2</sup>CH*Ar<sup>3</sup>) with high enantioselectivity (up to 97% ee). The reaction is assumed to proceed through <i>o</i>-quinone methide intermediates which undergo Rh-catalyzed asymmetric 1,4-addition of the arylboron reagents

    Rhodium-Catalyzed Asymmetric Arylation/Defluorination of 1‑(Trifluoromethyl)alkenes Forming Enantioenriched 1,1-Difluoroalkenes

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    The reaction of 1-(trifluoromethyl)­alkenes (CF<sub>3</sub>CH=CHR) with arylboroxines (ArBO)<sub>3</sub> in the presence of a chiral diene-rhodium catalyst gave high yields of chiral 1,1-difluoroalkenes (CF<sub>2</sub>=CHC*HArR) with high enantioselectivity (≥95% ee). The reaction is assumed to proceed through β-fluoride elimination of a β,β,β-trifluoroalkylrhodium intermediate that is generated by arylrhodation of the 1-(trifluoromethyl)­alkene

    Aryloxymethyltrifluoroborates for Rhodium-Catalyzed Asymmetric Conjugate Arylation. <i>o</i>‑Methoxyarylation through 1,4-Rhodium Shift

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    Reaction of potassium aryloxymethyltrifluoroborates <b>1</b> with α,β-unsaturated carbonyl compounds <b>2</b> in the presence of a chiral diene–rhodium catalyst in H<sub>2</sub>O at 100 °C introduced 2-methoxyaryl groups at the β-position of <b>2</b> with high enantioselectivity in high yields. The reaction is assumed to proceed through 1,4-Rh shift from aryloxymethyl-Rh intermediate to 2-methoxyaryl-Rh. The high availability of phenol derivatives makes this asymmetric conjugate arylation synthetically useful

    Asymmetric Synthesis of Triarylmethanes by Rhodium-Catalyzed Enantioselective Arylation of Diarylmethylamines with Arylboroxines

    No full text
    The reaction of racemic diarylmethylamines, (Ar<sup>1</sup>Ar<sup>2</sup>CHNR<sub>2</sub>), where Ar<sup>1</sup> is substituted with a 2-hydroxy group, with arylboroxines (Ar<sup>3</sup>BO)<sub>3</sub> in the presence of a chiral diene-rhodium catalyst gave high yields of chiral triarylmethanes (Ar<sup>1</sup>Ar<sup>2</sup>CH*Ar<sup>3</sup>) with high enantioselectivity (up to 97% ee). The reaction is assumed to proceed through <i>o</i>-quinone methide intermediates which undergo Rh-catalyzed asymmetric 1,4-addition of the arylboron reagents

    Aryloxymethyltrifluoroborates for Rhodium-Catalyzed Asymmetric Conjugate Arylation. <i>o</i>‑Methoxyarylation through 1,4-Rhodium Shift

    No full text
    Reaction of potassium aryloxymethyltrifluoroborates <b>1</b> with α,β-unsaturated carbonyl compounds <b>2</b> in the presence of a chiral diene–rhodium catalyst in H<sub>2</sub>O at 100 °C introduced 2-methoxyaryl groups at the β-position of <b>2</b> with high enantioselectivity in high yields. The reaction is assumed to proceed through 1,4-Rh shift from aryloxymethyl-Rh intermediate to 2-methoxyaryl-Rh. The high availability of phenol derivatives makes this asymmetric conjugate arylation synthetically useful

    Effect of Chiral Diene Ligands in Rhodium-Catalyzed Asymmetric Addition of Arylboronic Acids to α,β-Unsaturated Sulfonyl Compounds

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    Asymmetric addition of arylboronic acids to α,β-unsaturated sulfonyl compounds proceeded in the presence of a rhodium catalyst coordinated with a chiral diene ligand to give high yields of the addition products with high enantioselectivity (96–>99.5% ee). The diene ligand was proved to be essential for the formation of the addition products, while the use of a bisphosphine ligand mainly gave the <i>cine</i>-substitution product

    Palladium-Catalyzed Desymmetrization of Silacyclobutanes with Alkynes: Enantioselective Synthesis of Silicon-Stereogenic 1-Sila-2-cyclohexenes and Mechanistic Considerations

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    A palladium-catalyzed enantioselective desymmetrization of silacyclobutanes with alkynes has been developed to give silicon-stereogenic 1-sila-2-cyclohexenes with high enantioselectivity. The products thus obtained undergo further derivatizations with complete stereoselectivity, and a new catalytic cycle involving alkyne coordination (oxidative cyclization)–transmetalation (σ-bond metathesis)–reductive elimination has also been proposed

    The quality of information support analysis of business enterprises

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    В публікації розглядається основні характеристики інформаційного забезпечення діяльності підприємства.This publication is considered the main characteristics of the enterprise information supply

    Palladium-Catalyzed Desymmetrization of Silacyclobutanes with Alkynes: Enantioselective Synthesis of Silicon-Stereogenic 1-Sila-2-cyclohexenes and Mechanistic Considerations

    No full text
    A palladium-catalyzed enantioselective desymmetrization of silacyclobutanes with alkynes has been developed to give silicon-stereogenic 1-sila-2-cyclohexenes with high enantioselectivity. The products thus obtained undergo further derivatizations with complete stereoselectivity, and a new catalytic cycle involving alkyne coordination (oxidative cyclization)–transmetalation (σ-bond metathesis)–reductive elimination has also been proposed

    Enantioselective Synthesis of α‑Tri- and α‑Tetrasubstituted Allylsilanes by Copper-Catalyzed Asymmetric Allylic Substitution of Allyl Phosphates with Silylboronates

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    A copper/<i>N</i>-heterocyclic carbene-catalyzed asymmetric allylic substitution of allyl phosphates with a silylboronate has been developed to give highly enantioenriched allylsilanes. High regioselectivity has been achieved by employing NaOH as the base, and this catalyst system is effective for both γ-mono- and disubstituted allyl phosphates
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