Copper-Catalyzed Borylation of 2-Bromostyrenes via 1,3-Bromine and 1,4-Boryl Group Migrations
Year: 2026
Type: preprint
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.
Source: ChemRxiv
Authors: Go Yamagiwa, Kazuhiko Semba, Tetsuaki Fujihara
Institution: Kyoto University
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7223326175