10 research outputs found

    Arylboration of Alkenes by Cooperative Palladium/Copper Catalysis

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    Arylboration of vinylarenes and methyl crotonate with aryl halides and bis­(pinacolato)­diboron by cooperative Pd/Cu catalysis has been developed, giving 2-boryl-1,1-diarylethanes and an α-aryl-β-boryl ester in a regioselective manner. The reaction is compatible with a variety of functionalities and amenable to be scaled-up to a gram scale with no detriment to the yield. A short synthesis of the biologically active compound CDP840 was performed using the present reaction as a key step

    How to Control Inversion vs Retention Transmetalation between Pd<sup>II</sup>–Phenyl and Cu<sup>I</sup>–Alkyl Complexes: Theoretical Insight

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    Transmetalation between Pd­(Br)­(Ph<sup>A</sup>)­(PCyp<sub>3</sub>)<sub>2</sub> (Ph = phenyl, Cyp = cyclopentyl) and Cu­(C<sup>a</sup>HMePh<sup>B</sup>)­(NHC) (NHC = 1,3-bis­(2,6-diisopropylphenyl)-imidazolidin-2-ylidene) is an important elementary step in recently reported catalytic cross-coupling reaction by Pd/Cu cooperative system. DFT study discloses that the transmetalation occurs with inversion of the stereochemistry of the C<sup>a</sup>HMePh<sup>B</sup> group. In its transition state, the C<sup>a</sup>HMePh<sup>B</sup> group has almost planar structure around the C<sup>a</sup> atom. That planar geometry is stabilized by conjugation between the π* orbital of the Ph<sup>B</sup> and the 2p orbital of the C<sup>a</sup>. Another important factor is activation entropy (Δ<i>S</i>°<sup>‡</sup>); retention transmetalation occurs through Br-bridging transition state, which is less flexible than that of the inversion transmetalation because of the Br-bridging structure, leading to a smaller activation entropy in the retention transition state than in the inversion transition state. For C<sup>a</sup>HMeEt group, transmetalation occurs in a retention manner. In the planar C<sup>a</sup>HMeEt group of the inversion transition state, the C<sup>a</sup> 2p orbital cannot find a conjugation partner because of the absence of π-electron system in the C<sup>a</sup>HMeEt. Transmetalation of C<sup>a</sup>HMe­(CHCH<sub>2</sub>) occurs in a retention manner because the vinyl π* is less effective for the conjugation with the C<sup>a</sup> 2p because of its higher orbital energy than the Ph π*. The introduction of electron-withdrawing substituent on the Ph<sup>B</sup> is favorable for inversion transmetalation. These results suggest that the stereochemistry of the C<sup>a</sup> atom in transmetalation can be controlled by electronic effect of the C<sup>a</sup>HMeR (R = phenyl, vinyl, or alkyl) and sizes of the substituent and ligand

    How to Control Inversion vs Retention Transmetalation between Pd<sup>II</sup>–Phenyl and Cu<sup>I</sup>–Alkyl Complexes: Theoretical Insight

    No full text
    Transmetalation between Pd­(Br)­(Ph<sup>A</sup>)­(PCyp<sub>3</sub>)<sub>2</sub> (Ph = phenyl, Cyp = cyclopentyl) and Cu­(C<sup>a</sup>HMePh<sup>B</sup>)­(NHC) (NHC = 1,3-bis­(2,6-diisopropylphenyl)-imidazolidin-2-ylidene) is an important elementary step in recently reported catalytic cross-coupling reaction by Pd/Cu cooperative system. DFT study discloses that the transmetalation occurs with inversion of the stereochemistry of the C<sup>a</sup>HMePh<sup>B</sup> group. In its transition state, the C<sup>a</sup>HMePh<sup>B</sup> group has almost planar structure around the C<sup>a</sup> atom. That planar geometry is stabilized by conjugation between the π* orbital of the Ph<sup>B</sup> and the 2p orbital of the C<sup>a</sup>. Another important factor is activation entropy (Δ<i>S</i>°<sup>‡</sup>); retention transmetalation occurs through Br-bridging transition state, which is less flexible than that of the inversion transmetalation because of the Br-bridging structure, leading to a smaller activation entropy in the retention transition state than in the inversion transition state. For C<sup>a</sup>HMeEt group, transmetalation occurs in a retention manner. In the planar C<sup>a</sup>HMeEt group of the inversion transition state, the C<sup>a</sup> 2p orbital cannot find a conjugation partner because of the absence of π-electron system in the C<sup>a</sup>HMeEt. Transmetalation of C<sup>a</sup>HMe­(CHCH<sub>2</sub>) occurs in a retention manner because the vinyl π* is less effective for the conjugation with the C<sup>a</sup> 2p because of its higher orbital energy than the Ph π*. The introduction of electron-withdrawing substituent on the Ph<sup>B</sup> is favorable for inversion transmetalation. These results suggest that the stereochemistry of the C<sup>a</sup> atom in transmetalation can be controlled by electronic effect of the C<sup>a</sup>HMeR (R = phenyl, vinyl, or alkyl) and sizes of the substituent and ligand

    Intramolecular Aminocyanation of Alkenes by Cooperative Palladium/Boron Catalysis

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    A cooperative palladium/triorganoboron catalyst to accomplish the intramolecular aminocyanation of alkenes through the cleavage of N–CN bonds is reported. 4,5-Bis­(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) is found to be crucial as a ligand for palladium to effectively catalyze the transformation with high chemo- and regioselectivity. A range of substituted indolines and pyrrolidines with both tetra- or trisubstituted carbon and cyano functionalities are readily furnished by the newly developed cyanofunctionalization reaction. A preliminary example of enantioselective aminocyanation is also described

    <i>para</i>-Selective Alkylation of Benzamides and Aromatic Ketones by Cooperative Nickel/Aluminum Catalysis

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    We report a method that ensures the selective alkylation of benzamides and aromatic ketones at the <i>para</i>-position via cooperative nickel/aluminum catalysis. Using a bulky catalyst/cocatalyst system allows reactions between benzamides and alkenes to afford the corresponding <i>para</i>-alkylated products. The origin of the high <i>para</i>-selectivity has also been investigated by density functional theory calculations

    Rhodium Complexes Bearing PAlP Pincer Ligands

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    We report rhodium complexes bearing PAlP pincer ligands with an X-type aluminyl moiety. IR spectroscopy and single-crystal X-ray diffraction analysis of a carbonyl complex exhibit the considerable σ-donating ability of the aluminyl ligand, whose Lewis acidity is confirmed through coordination of pyridine to the aluminum center. The X-type PAlP–Rh complexes catalyze C2-selective monoalkylation of pyridine with alkenes

    Rhodium Complexes Bearing PAlP Pincer Ligands

    No full text
    We report rhodium complexes bearing PAlP pincer ligands with an X-type aluminyl moiety. IR spectroscopy and single-crystal X-ray diffraction analysis of a carbonyl complex exhibit the considerable σ-donating ability of the aluminyl ligand, whose Lewis acidity is confirmed through coordination of pyridine to the aluminum center. The X-type PAlP–Rh complexes catalyze C2-selective monoalkylation of pyridine with alkenes

    Rhodium Complexes Bearing PAlP Pincer Ligands

    No full text
    We report rhodium complexes bearing PAlP pincer ligands with an X-type aluminyl moiety. IR spectroscopy and single-crystal X-ray diffraction analysis of a carbonyl complex exhibit the considerable σ-donating ability of the aluminyl ligand, whose Lewis acidity is confirmed through coordination of pyridine to the aluminum center. The X-type PAlP–Rh complexes catalyze C2-selective monoalkylation of pyridine with alkenes

    Rhodium Complexes Bearing PAlP Pincer Ligands

    No full text
    We report rhodium complexes bearing PAlP pincer ligands with an X-type aluminyl moiety. IR spectroscopy and single-crystal X-ray diffraction analysis of a carbonyl complex exhibit the considerable σ-donating ability of the aluminyl ligand, whose Lewis acidity is confirmed through coordination of pyridine to the aluminum center. The X-type PAlP–Rh complexes catalyze C2-selective monoalkylation of pyridine with alkenes
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