Copper-Catalyzed Borylation of 2-Bromostyrenes via 1,3-Bromine and 1,4-Boryl Group Migrations
- 1Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering
- 2Kyoto University
- 3Graduate School of Engineering
Abstract
Arylboronates are valuable synthetic intermediates for constructing C–C and C–X bonds. While the coppercatalyzed borylation of aryl halides has been reported, synthesizing 2-borylstyrenes from the corresponding aryl halides remains a challenge because the alkene is incompatible with conventional borylation methods. Herein, we turn this side reaction into the trigger of a productive cascade, enabling the copper-catalyzed borylation of 2-bromostyrenes with diboron reagents. The sequence comprises borylcupration, 1,3-bromine migration to form an arylcopper, intramolecular attack of the arylcopper on boron to give a cyclic borate, and copper-assisted debromination that restores the alkenyl group. Overall, the boryl group undergoes a 1,4-migration from C(sp3) to C(sp2), with the alkene serving as a transient relay. The detailed reaction mechanism for 1,4-boryl group migration was revealed by using density functional theory (DFT) calculations. The reaction tolerates chloro substituent and borylates dibromostyrenes site-selectively and is readily scalable to the gram scale.
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BibTeX
@misc{yamagiwa2026coppercatalyzed,
title = {{Copper-Catalyzed Borylation of 2-Bromostyrenes via 1,3-Bromine and 1,4-Boryl Group Migrations}},
author = {Go Yamagiwa and Kazuhiko Semba and Tetsuaki Fujihara},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010958/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010958/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Copper-Catalyzed Borylation of 2-Bromostyrenes via 1,3-Bromine and 1,4-Boryl Group Migrations
AU - Go Yamagiwa
AU - Kazuhiko Semba
AU - Tetsuaki Fujihara
PY - 2026
DA - 2026/10/23
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010958/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010958/v1
AB - Arylboronates are valuable synthetic intermediates for constructing C–C and C–X bonds. While the coppercatalyzed borylation of aryl halides has been reported, synthesizing 2-borylstyrenes from the corresponding aryl halides remains a challenge because the alkene is incompatible with conventional borylation methods. Herein, we turn this side reaction into the trigger of a productive cascade, enabling the copper-catalyzed borylation of 2-bromostyrenes with diboron reagents. The sequence comprises borylcupration, 1,3-bromine migration to form an arylcopper, intramolecular attack of the arylcopper on boron to give a cyclic borate, and copper-assisted debromination that restores the alkenyl group. Overall, the boryl group undergoes a 1,4-migration from C(sp3) to C(sp2), with the alkene serving as a transient relay. The detailed reaction mechanism for 1,4-boryl group migration was revealed by using density functional theory (DFT) calculations. The reaction tolerates chloro substituent and borylates dibromostyrenes site-selectively and is readily scalable to the gram scale.
ER -