Theoretical study of reaction pathways for the rhodium phosphine-catalysed borylation of C–H bonds with pinacolborane
作者： Wai Han Lam , King Chung Lam , Zhenyang Lin , Shigeru Shimada , Robin N. Perutz
DOI: 10.1039/B402632B
关键词: Reductive elimination 、 Reaction mechanism 、 Medicinal chemistry 、 Electrophile 、 Borylation 、 Chemistry 、 Rhodium 、 Phosphine 、 Catalysis 、 Stereochemistry 、 Regioselectivity
摘要: The reaction mechanism of the rhodium–phosphine catalysed borylation methyl-substituted arenes using pinacolborane (HBpin) has been investigated theoretically DFT calculations at B3PW91 level. Factors affecting selectivity for benzylic vs. aromatic C–H bond activation have examined. It was found that [Rh(PR3)2(H)] is active species which oxidatively adds leading to an η3-benzyl complex key determining unusual regioselectivity observed experimentally this catalyst system. Subsequent with HBpin leads a [Rh(PR3)2(η3-benzyl)(H)(Bpin)] from B–C reductive elimination provides product and regenerates catalyst. electrophilic nature boryl ligand assists in process. In contrast Ir(L)2(boryl)3-based catalysts, Ir(III)–Ir(V) cycles proposed, Rh(I)–Rh(III) cycle operating system addressed herein.
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