Dinuclear Tetrapyrazolyl Palladium Complexes Exhibiting Facile Tandem Transfer Hydrogenation/Suzuki Coupling Reaction of Fluoroarylketone
KAUST DepartmentKAUST Catalysis Center (KCC)
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AbstractHerein, we report an unprecedented example of dinuclear pyrazolyl-based Pd complexes exhibiting facile tandem catalysis for fluoroarylketone: Tetrapyrazolyl di-palladium complexes with varying Pd-Pd distances efficiently catalyze the tandem reaction involving transfer hydrogenation of fluoroarylketone to the corresponding alcohol and Suzuki-Miyaura cross coupling reaction of the resulting fluoroarylalcohol under moderate reaction conditions, to biaryl alcohol. The complex with the shortest Pd-Pd distance exhibits the highest tandem activity among its di-metallic analogues, and exceeds in terms of activity and selectivity the analogous mononuclear compound. The kinetics of the reaction indicates clearly that reductive transformation of haloarylketone into haloaryalcohol is the rate determining step in the tandem reaction. Interestingly while fluoroarylketone undergoes the multistep tandem catalysis, the chloro- and bromo-arylketones undergo only a single step C-C coupling reaction resulting in biarylketone as the final product. Unlike the pyrazole based Pd compounds, the precursor PdCl2 and the phosphine based relevant complexes (PPh3)2PdCl2 and (PPh3)4Pd are found to be unable to exhibit the tandem catalysis.
CitationDinuclear Tetrapyrazolyl Palladium Complexes Exhibiting Facile Tandem Transfer Hydrogenation/Suzuki Coupling Reaction of Fluoroarylketone 2016 ACS Catalysis
SponsorsThis work has been supported by DST (EMR/2015/002219), New Delhi, India. ND and SKT are grateful to the University Grant Commission (UGC) and the Council of Scientific and Industrial Research (CSIR), New Delhi, India, respectively, for their fellowship. N. M. acknowledges the King Abdullah University of Science and Technology (KAUST) for the postdoctoral fellowship. The authors are grateful to the reviewers’ for their valuable comments and suggestions to improve the manuscript.
PublisherAmerican Chemical Society (ACS)