Optimization of signal amplification by reversible exchange for polarization of tridentate chelating bis[(2-pyridyl)alkyl]amine

Vinyl fluorides play an important role in drug development as they serve as bioisosteres for peptide bonds and are found in a range of biologically active molecules. The discovery of safe, general and practical procedures to prepare vinyl fluorides remains an important goal and challenge for synthetic chemistry. Here we introduce an inexpensive and easily-handled reagent and report simple, scalable, and metal-free protocols for the regioselective and stereodivergent hydrofluorination of alkynes to access both the E and Z isomers of vinyl fluorides. These conditions were suitable for a diverse collection of alkynes, including several highly-functionalized pharmaceutical derivatives. Mechanistic and DFT studies support C–F bond formation through a vinyl cation intermediate, with the (E)- and (Z)-hydrofluorination products forming under kinetic and thermodynamic control, respectively.

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Copper Catalyzed sp3 C-H α-Acetylation

10.26434/chemrxiv.11407116.v1 ◽

2019 ◽

Author(s):

Otome Okoromoba ◽

Eun Sil Jang ◽

Claire McMullin ◽

Thomas Cundari ◽

Timothy H. Warren

Keyword(s):

Natural Products ◽

Dft Studies ◽

Alkyl Radicals ◽

Important Chemical ◽

Alkyl Electrophiles ◽

Synthetic Intermediates ◽

Alkylation Reactions

α-substituted ketones are important chemical targets as synthetic intermediates as well as functionalities in in natural products and pharmaceuticals. We report the sp3 C-H α-acetylation of sp3 C-H substrates R-H with arylmethyl ketones ArC(O)Me to provide α-alkylated ketones ArC(O)CH2R at RT with tBuOOtBu as oxidant via copper(I) β-diketiminato catalysts. Proceeding via alkyl radicals R•, this method enables α-substitution with bulky substituents without competing elimination that occurs in more traditional alkylation reactions between enolates and alkyl electrophiles. DFT studies suggest the intermediacy of copper(II) enolates [CuII](CH2C(O)Ar) that capture alkyl radicals R• to give R-CH2C(O)Ar under competing dimerization of the copper(II) enolate to give the 1,4-diketone ArC(O)CH2CH2C(O)Ar.

Download Full-text

Copper Catalyzed sp3 C-H α-Acetylation

10.26434/chemrxiv.11407116 ◽

2019 ◽

Author(s):

Otome Okoromoba ◽

Eun Sil Jang ◽

Claire McMullin ◽

Thomas Cundari ◽

Timothy H. Warren

Keyword(s):

Natural Products ◽

Dft Studies ◽

Alkyl Radicals ◽

Important Chemical ◽

Alkyl Electrophiles ◽

Synthetic Intermediates ◽

Alkylation Reactions

α-substituted ketones are important chemical targets as synthetic intermediates as well as functionalities in in natural products and pharmaceuticals. We report the sp3 C-H α-acetylation of sp3 C-H substrates R-H with arylmethyl ketones ArC(O)Me to provide α-alkylated ketones ArC(O)CH2R at RT with tBuOOtBu as oxidant via copper(I) β-diketiminato catalysts. Proceeding via alkyl radicals R•, this method enables α-substitution with bulky substituents without competing elimination that occurs in more traditional alkylation reactions between enolates and alkyl electrophiles. DFT studies suggest the intermediacy of copper(II) enolates [CuII](CH2C(O)Ar) that capture alkyl radicals R• to give R-CH2C(O)Ar under competing dimerization of the copper(II) enolate to give the 1,4-diketone ArC(O)CH2CH2C(O)Ar.

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