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Halogen–Sodium Exchange Revisited

preprint
submitted on 27.05.2020 and posted on 29.05.2020 by Sobi Asako, Ikko Takahashi, Hirotaka Nakajima, Laurean Ilies, Kazuhiko Takai

Sodium is the most abundant alkali metal on Earth. Despite being an attractive choice for sustainable synthesis, organosodium compounds are rarely used in organic synthesis and have been overshadowed to date by organolithium compounds. This situation is largely due to the lack of convenient and efficient methods for the preparation of organosodium compounds. We report herein a halogen–sodium exchange method to prepare a large variety of (hetero)aryl- and alkenylsodium compounds, many of them previously inaccessible by other methods. The key discovery is the use of a bulky alkylsodium lacking a β-hydrogen, readily prepared in situ from neopentyl chloride and an easy-to-handle sodium dispersion, which retards undesired reactions such as Wurtz–Fittig coupling and β-hydrogen elimination, and enables efficient halogen-sodium exchange. We believe that the efficiency, generality, and convenience of the present method will open new horizons for the use of organosodium in organic synthesis, ultimately contributing to the development of sustainable chemistry by replacing the currently dominant organolithium reagents.

History

Email Address of Submitting Author

sobi.asako@riken.jp

Institution

RIKEN Center for Sustainable Resource Science

Country

Japan

ORCID For Submitting Author

0000-0003-4525-5317

Declaration of Conflict of Interest

We thank Okayama University, RIKEN, and KOBELCO ECO-Solutions CO., Ltd. for financial support. Sodium dispersion was provided by KOBELCO ECO-Solutions Co., Ltd. S.A. and K.T. are listed as inventors on patent applications (PCT/JP2019/033980) that cover the halogen-sodium exchange reactions presented in this paper.

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