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Ligand-Free Iron-Catalyzed Regiodivergent Hydroboration of Unactivated Terminal Alkenes

preprint
submitted on 02.01.2020 and posted on 07.01.2020 by Wei Su, Ruixiao Qiao, Xiaoli Zheng, Xia Tian, Jianrong Han, Shiming Fan, Qiushi Cheng, Shouxin Liu
The control of regioselectivities has been recognized as the elementary issue for alkene hydroboration. Despite considerable progress, the specificity of alkene substrates or the adjustment of ligands were necessary for specific regioselectivities, which restrict the universality and practicability. Herein, we report a ligand-free iron-catalyzed regiodivergent hydroboration of unactivated terminal alkenes that obtains both Markovnikov and anti-Markovnikov hydroboration products in excellent regioselectivities. Notably, solvents and bases were shown to be crucial factors influencing the regioselectivities and further studies suggested the iron-boron alkoxide ate complex is the key intermediate that determines the unusual Markovnikov regioselectivity. Terminal alkenes with diverse structures (mono-substituted and 1,1-disubstituted, open-chain and exocyclic) underwent the transformation smoothly. The reaction does not require the addition of auxiliary ligands and it can be performed on a gram scale, thus providing an efficient and sustainable method for the synthesis of primary, secondary, and tertiary alkyl borates.

History

Email Address of Submitting Author

weisu@hebust.edu.cn

Institution

Hebei University of Science and Technology

Country

China

ORCID For Submitting Author

0000-0002-6487-9339

Declaration of Conflict of Interest

The authors declare no competing financial interest.

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