A General Method to Access Sterically Encumbered Geminal Bis(boronates) via Formal Umpolung Transformation of Terminal Diboron Compounds

Peng-Fei Ning, Yi Wei, Xin-Yi Chen, Yi-Fei Yang, Feng-Chen Gao, Kai Hong*

*School of Chemistry and Molecular Engineering, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, China, Email: khongchem.ecnu.edu.cn

P.-F. Ning, Y. Wei, X.-Y. Chen, Y.-F. Yang, F.-C. Gao, K. Hong, Angew. Chem. Int. Ed., 2023, 62, e202315232.

DOI: 10.1002/anie.202315232

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Abstract

A general method for accessing sterically encumbered geminal bis(boronates) is based on a formal umpolung strategy. Readily available 1,1-diborylalkanes were first converted into the corresponding α-halogenated derivatives, which then serve as electrophilic components, undergoing a formal substitution with a diverse array of nucleophiles to form a series of C−C, C−O, C−S, and C−N bonds.

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Reaction of α-halogenated geminal bis(boronates) and Grignard reagents

In an argon-filled glove box, to a 15 mL vial equipped with a magnetic stir bar was added α-halogenated geminal bis(boronate) (0.2 mmol, 1.0 equiv.). The vial was sealed with a polypropylene open-top cap with PTFE/silicone septum, then removed from the glove box. 1,4-Dioxane (2.0 mL) was added and the vial was cooled in an ice-cold water bath. Grignard reagent (0.30 mmol, 1.5 equiv.) was slowly added before THF/1,4-dioxane froze. The mixture was then warmed to room temperature and stirred for 2 hours. Upon completion, the reaction was quenched with sat. NH₄Cl solution (4 mL) and extracted with Et₂O (3 x 10 mL). The combined organic layers were dried over Na₂SO₄, filtered, and concentrated under reduced pressure, and the crude reaction mixture was purified by column chromatography on pre-dried silica gel.

Construction of α-Halogenated Boronic Esters via Visible Light-Induced C-H Bromination

F.-C. Gao, M. Li, H.-Y. Gu, X.-Y. Chen, S. Xu, Y. Wei, K. Hong, J. Org. Chem., 2023, 88, 14246-14254.

Key Words

1,1-diboronates, alkylboronates, benzylboronates, Grignard reaction

ID: J06-Y2023