Room temperature catalytic carbon-hydrogen bond alumination of unactivated arenes: mechanism and selectivity
Thomas N Hooper1, Martí Garçon1, Andrew J P White1
1Department of Chemistry , Imperial College London , South Kensington , London , SW7 2AZ , UK .
Abstract:
We report the first catalytic methods for the transformation of C-H bonds of unactivated arenes into C-Al bonds. The catalytic reactions occur at 25 °C (benzene, toluene and xylenes) with palladium loadings as low as 0.1 mol%. Remarkably, the C-H activation of toluene and xylenes proceeds with ortho- and meta-selectivity. This selectivity is highly unusual and complementary to both Friedel-Crafts and the majority of C-H borylation methods. Through a detailed mechanistic analysis (Eyring analysis, KIE, DFT, QTAIM) we show that unusual Pd-Al intermetallic complexes are on the catalytic cycle and that the selectivity is determined by weak attractive dispersion forces in the transition state for C-H bond breaking.
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