- Neopentylglycolborylation of ortho -substituted aryl halides catalyzed by NiCl2-Based mixed-ligand systems
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NiCl2-based mixed-ligand systems were shown to be very effective catalysts for the neopentylglycolborylation of aryl iodides, bromides, and chlorides bearing electron-rich and electron-deficient ortho-substituents. Although NiCl2-based single-ligand catalytic systems were able to mediate neopentylglycolborylation of selected substrates, they were not as effective for all substrates, highlighting the value of the mixed-ligand concept. Optimization of the Ni(II)-catalyzed neopentylglycolborylation of 2-iodoanisole and methyl 2-iodobenzoate demonstrated that, while the role of ligand and coligand in the conversion of Ni(II) precatalyst to Ni(0) active catalyst cannot be ignored, a mixed-ligand complex is likely present throughout the catalytic cycle. In addition, protodeborylation and hydrodehalogenation were demonstrated to be the predominant side reactions of Ni(II)-catalyzed borylation of ortho-substituted aryl halides containing the electron-deficient carboxylate substituents. Ni(II) complexes in the presence of H2O and Ni(0) are responsible for the catalysis of these side reactions.
- Moldoveanu, Costel,Wilson, Daniela A.,Wilson, Christopher J.,Leowanawat, Pawaret,Resmerita, Ana-Maria,Liu, Chi,Rosen, Brad M.,Percec, Virgil
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supporting information; experimental part
p. 5438 - 5452
(2010/11/05)
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- Synthesis of Ortho Substituted Arylboronic Esters by in Situ Trapping of Unstable Lithio Intermediates
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matrix presented Ortho lithiation-in situ boration using lithium 2,2,6,6-tetramethylpiperidide (LTMP) in combination with triisopropylborate (B(OiPr)3) is a highly efficient and experimentally straightforward process for the preparation of ortho substituted arylboronic esters. The mild reaction conditions allow the presence of functionalities such as ester or cyano groups or halogen substituents that are usually not compatible with the conditions used in directed ortho metalation of arenes. The arylboronic esters underwent Suzuki-type cross-coupling with a range of aryl halides, furnishing biaryls in 53-94% yield.
- Kristensen, Jesper,Lysen, Morten,Vedso, Per,Begtrup, Mikael
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p. 1435 - 1437
(2007/10/03)
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