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2.6.1.3 Carboxylation of Organoboron Reagents Catalyzed by N-Heterocyclic Carbene–Copper Complexes

DOI: 10.1055/sos-SD-224-00164

Nelson, D. J.Science of Synthesis: N-Heterocyclic Carbenes in Catalytic Organic Synthesis, (20162284.

The carboxylation of boronic esters has been reported by Hou and co-workers. The reaction, catalyzed by [1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]copper(I) chloride [CuCl(IPr)], which presumably forms Cu(Ot-Bu)(IPr) in situ, proceeds by transmetalation from boron to copper, followed by insertion of carbon dioxide into the Cu—C bond thus formed, as tested by stoichiometric experiments. Quite a wide range of aryl- and vinylboronic acid 2,2-dimethylpropane-1,3-diol esters 8 undergo reaction to form the corresponding carboxylic acids 9 (Scheme 4).[‌6‌] The same group reported subsequently that 9-borabicyclo[3.3.1]nonane compounds also undergo carboxylation successfully, allowing the development of a one-pot alkene hydroboration/carboxylation procedure.[‌7‌] Duong and co-workers have reported an analogous methodology for the carboxylation of allylboronates.[‌8‌]

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References


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