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Updated: May 20, 2026

Synthesis of a Borylated Ibuprofen Derivative Through Suzuki Cross-Coupling and Alkene Boracarboxylation Reactions
Published on: November 30, 2022
Synthesis, coupling, and condensation reactions of 1,2-diborylated benzenes: an experimental and quantum-chemical
Ömer Seven1, Zheng-Wang Qu, Hui Zhu
1Institut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt, Max-von-Laue-Straße 7, 60438 Frankfurt am Main, Germany.
Abstract:
1,2-Bis(pinacolboryl)benzene (1,2-C(6)H(4) (Bpin)(2), 2) was synthesized in preparatively useful yields from 1,2-C(6)H(4)Br(2), iPrO-Bpin, and Mg turnings in the presence of 1,2-C(2)H(4)Br(2) as an entrainer. Compound 2 is a versatile starting material for the synthesis of (un)symmetrically substituted benzenes (i.e., 1,2-C(6)H(4)(Ar(1))(Ar(2))) through sequential Suzuki-Miyaura coupling reactions. Alternatively, it can be transformed into bis-borate Li(2)[1,2-C(6)H(4)(BH(3))(2)] (3) through reduction with Li[AlH(4)]. In the crystal lattice, the diethyl ether solvate 3·OEt(2) establishes a columnar structure that is reinforced by an intricate network of B-(μ-H)-Li interactions. Hydride-abstraction from compound 3 with Me(3)SiCl leads to the transient ditopic borane 1,2-C(6)H(4)(BH(2))(2), which can either be used in situ for subsequent hydroboration reactions or trapped as its stable NMe(2)Et diadduct (6). In SMe(2) solution, the putative diadduct 1,2-C(6)H(4)(BH(2)·SMe(2))(2) is not long-term stable but rather undergoes a condensation reaction to give 9,10-dihydro-9,10-diboraanthracene, HB(μ-C(6)H(4))(2)BH, and BH(3). 9,10-Dihydro-9,10-diboraanthracene was isolated from the reaction mixture as its SMe(2) monoadduct (7), which dimerizes in the solid state through two B-H-B bridges ((7)(2), elucidated by X-ray crystallography). In contrast, hydride-abstraction from compound 3 in THF or CH(2)Cl(2) provides the unique exo-adduct H(2)B(μ-H)(2)B(μ-C(6)H(4))(2)B(μ-H)(2)BH(2) (8, elucidated by X-ray crystallography). Quantum-chemical calculations on various conceivable isomers of [1,2-C(6)H(4)(BH(2))(2)](2) revealed that compound 8 was the most stable of these species. Moreover, the calculations confirmed the experimental findings that the NMe(2)Et diadduct of 1,2-C(6)H(4)(BH(2))(2) is significantly more stable than the corresponding SMe(2) complex and that the latter complex is not able to compete successfully with borane-dimerization and -condensation. The reaction cascade in SMe(2), which proceeds from 1,2-C(6)H(4)(BH(2))(2) to the observed adducts of HB(μ-C(6)H(4))(2)BH, has been elucidated in detail and the important role of B-C-B-bridged intermediates has been firmly established.
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