Pd‐PEPPSI‐IPent‐SiO2: A Supported Catalyst for Challenging Negishi Coupling Reactions in Flow

A silica‐supported precatalyst, Pd‐PEPPSI‐IPent‐SiO2, has been prepared and evaluated for its proficiency in the Negishi cross‐coupling of hindered and electronically deactivated coupling partners. The precatalyst Pd‐PEPPSI‐IPent loaded onto packed bed columns shows high catalytic activity for the r...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2017-10, Vol.56 (43), p.13347-13350
Main Authors: Price, Gregory A., Hassan, Abbas, Chandrasoma, Nalin, Bogdan, Andrew R., Djuric, Stevan W., Organ, Michael G.
Format: Article
Language:English
Subjects:
arenes
Aromatic compounds
Catalysis
Catalytic activity
Chemical reactions
Couplings
Cross coupling
Deactivation
flow chemistry
N-heterocyclic carbenes
palladium
Reagents
Selectivity
Silica
Silicon dioxide
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Summary:A silica‐supported precatalyst, Pd‐PEPPSI‐IPent‐SiO2, has been prepared and evaluated for its proficiency in the Negishi cross‐coupling of hindered and electronically deactivated coupling partners. The precatalyst Pd‐PEPPSI‐IPent loaded onto packed bed columns shows high catalytic activity for the room‐temperature coupling of deactivated/hindered biaryl partners. Also for the first time, the flowed Csp3–Csp2 coupling of secondary alkylzinc reagents to (hetero)aromatics has been achieved with high selectivity with Pd‐PEPPSI‐IPent‐SiO2. These couplings required residence times as short as 3 minutes to effect completion of these challenging transformations with excellent selectivity for the nonrearranged product. Scratching the surface: The Pd‐PEPPSI‐IPent precatalyst was attached to the surface of silica and loaded into packed‐bed flow columns. The catalyst system displays extremely high reactivity for the room‐temperature coupling of secondary alkylzinc reagents to heterocycles. The reactions feature fast residence times (ca. 3 to 20 min), high conversions, and excellent selectivity. The resulting products are undergoing evaluation in medicinal chemistry.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201708598