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J Am Chem Soc . 2020 Jun 24

σ-Bond Hydroboration of Cyclopropanes

Branko Cirovic, L Charlotte J de Bree, Laszlo Groh, Bas A Blok, Joyce Chan, Walter J F M van der Velden, M E J Bremmers, Reinout van Crevel, Kristian Händler, Simone Picelli, Jonas Schulte-Schrepping, Kathrin Klee, Marije Oosting, Valerie A C M Koeken, Jakko van Ingen, Yang Li, Christine S Benn, Joachim L Schultze, Leo A B Joosten, Nigel Curtis, Mihai G Netea, Andreas Schlitzer, Maria Elisa Mancuso, Johannes Oldenburg, Lisa Boggio, Gili Kenet, Anthony Chan, Carmen Altisent, Wilfried Seifert, Elena Santagostino, Michael Marleaux, Kanchan Anand, Eicke Latz, Matthias Geyer, WHO Working Group on the Clinical Characterisation and Management of COVID-19 infection, Hiroki Kondo, Shin Miyamura, Kaoru Matsushita, Hiroki Kato, Chisa Kobayashi, Arifin, Kenichiro Itami, Daisuke Yokogawa, Junichiro Yamaguchi

Hydroboration of alkenes is a classical reaction in organic synthesis in which alkenes react with boranes to give alkylboranes with subsequent oxidation resulting in alcohols. The double bond (π-bond) of alkenes can be readily reacted with boranes owing to its high reactivity. However, the single bond (σ-bond) of alkanes has never been reacted. To pursue the development of σ-bond cleavage, we selected cyclopropanes as model substrates since they present a relatively weak σ-bond. Herein, we describe an iridium-catalyzed hydroboration of cyclopropanes, resulting in β-methyl alkylboronates. These unusually branched boronates can be derivatized by oxidation or cross-coupling chemistry, accessing "designer" products that are desired by practitioners of natural product synthesis and medicinal chemistry. Furthermore, mechanistic investigations and theoretical studies revealed the enabling role of the catalyst.

PMID: 32539357