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Synthesis of a Borylated Ibuprofen Derivative Through Suzuki Cross-Coupling and Alkene Boracarboxylation Reactions
Published on: November 30, 2022
Direct C-H Borylation of Arenes Catalyzed by Saturated Hydride-Boryl-Iridium-POP Complexes: Kinetic Analysis of the
Miguel A Esteruelas1, Antonio Martínez1, Montserrat Oliván1
1Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), Centro de Innovación en Química Avanzada (ORFEO-CINQA), Universidad de Zaragoza-CSIC, 50009, Zaragoza, Spain.
Abstract:
The saturated trihydride IrH3 {κ3 -P,O,P-[xant(PiPr2 )2 ]} (1; xant(PiPr2 )2 =9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene) activates the B-H bond of two molecules of pinacolborane (HBpin) to give H2 , the hydride-boryl derivatives IrH2 (Bpin){κ3 -P,O,P-[xant(PiPr2 )2 ]} (2) and IrH(Bpin)2 {κ3 -P,O,P-[xant(PiPr2 )2 ]} (3) in a sequential manner. Complex 3 activates a C-H bond of two molecules of benzene to form PhBpin and regenerates 2 and 1, also in a sequential manner. Thus, complexes 1, 2, and 3 define two cycles for the catalytic direct C-H borylation of arenes with HBpin, which have dihydride 2 as a common intermediate. C-H bond activation of the arenes is the rate-determining step of both cycles, as the C-H oxidative addition to 3 is faster than to 2. The results from a kinetic study of the reactions of 1 and 2 with HBpin support a cooperative function of the hydride ligands in the B-H bond activation. The addition of the boron atom of the borane to a hydride facilitates the coordination of the B-H bond through the formation of κ1 - and κ2 -dihydrideborate intermediates.
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