Cobalt-Catalyzed Enantioselective Hydroboration of α-Substituted Acrylates
Manoj D. Patil, Kiron Kumar Ghosh, T. V. RajanBabu*
*Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, United States,
Email: rajanbabu.1
osu.edu
M. D. Patil, K. K. Ghosh, T. V. RajanBabu, J. Am. Chem. Soc., 2024, 146, 6604-6617.
DOI: 10.1021/jacs.3c12020
Abstract
Cobalt catalysis enables mild reaction conditions for efficient and highly regio- and enantioselective hydroboration of α-alkyl- and α-aryl- acrylates, giving β-borylated propionates. These intermediates could serve as valuable chiral synthons, some from feedstock carbon sources, for the synthesis of propionate-bearing motifs including polyketides and related molecules.
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Details
The article discusses a novel cobalt-catalyzed enantioselective hydroboration of α-substituted acrylates, focusing on α-alkyl and α-aryl acrylates. This method addresses the limitations of previous metal-catalyzed hydroborations, which primarily used rhodium catalysts and lacked examples for α-arylacrylic acid esters. The researchers identified 2-(2-diarylphosphinophenyl)oxazoline ligands and mild reaction conditions that enable efficient and highly regio- and enantioselective hydroboration, producing β-borylated propionates. These intermediates are valuable chiral synthons for synthesizing propionate-bearing motifs, including polyketides and medicinal compounds. The study highlights the synthesis of the "Roche" ester and tropic acid esters, demonstrating the method's practical applications. Mechanistic studies suggest the necessity of a cationic Co(I) species as the catalyst, proposing an oxidative migration mechanism rather than a Co-H initiated route. The research emphasizes the potential of earth-abundant cobalt catalysts in organic transformations, offering a cost-effective and scalable alternative to precious metal catalysts. The findings contribute significantly to the field of asymmetric hydroboration, providing new pathways for synthesizing chiral compounds with broad applications in pharmaceuticals and organic synthesis.
Key Words
ID: J48-Y2024
