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Lookup NU author(s): Dr Simon DohertyORCiD, Dr Julian Knight, Tom Backhouse, Dr Andrew Bradford
Palladium nanoparticles stabilized by lightly cross-linked phosphine-decorated polymer immobilized ionic liquids (PIIL) and their PEGylated counterparts (PEGPIIL) are highly effective catalysts for the aqueous phase hydrogenation and sodium borohydride-based reduction of a wide range of nitroaromatic and heteroaromatic compounds under mild conditions with low catalyst loadings. Introduction of extensive cross-linking with tris(4-vinylphenyl)phosphine to isolate the phosphine-based heteroatom and limit the number of surface Pd----P interactions did not have a significant influence on catalyst performance. Comparative testing revealed PdNPs immobilized on lightly cross-linked phsophine-decoarted PEGylated polymer to be a highly efficient catalyst for the aqueous phase reduction of nitroarenes with a TON of 36,000 (TOF = 2,580 h-1) for hydrogenation and a TON of 274,000 (TOF = 17,125 h‑1) for transfer hydrogenation. Even though these reactions occur under diffusion control due the poor solubility of the substrate these values are the highest to be reported for the room temperature aqueous phase reduction of nitroarenes catalyzed by a nanoparticle-based system. A continuous flow reduction of nitrobenzene in a packed bed reactor operated over a period of 250 min with no sign of catalyst deactivation and the corresponding space-time-yield of 0.738 g L-1 min-1 is a marked improvement on that of 0.384 g L-1 min-1 obtained in batch. The same system also catalyzes a tandem Suzuki-Miyaura cross coupling-nitroarene reduction sequence to afford high yields of biaryl amine in an operationally straightforward single-pot procedure. This is a highly versatile protocol which will enable the aromatic nitro fragment to be introduced as a nitro-substituted aryl or heteroaryl halide and as such will lend itself to rapid diversification for the synthesis of a wide range of amines.
Author(s): Doherty S, Knight JG, Backhouse T, Bradford A, Saunders, Bourne RA, Chamberlain TW, Stones R, Clayton A, Lovelock K
Publication type: Article
Publication status: Published
Journal: Catalysis, Science & Technology
Year: 2018
Volume: 8
Issue: 5
Pages: 1454-1467
Print publication date: 07/03/2018
Online publication date: 08/02/2018
Acceptance date: 07/02/2018
Date deposited: 05/02/2018
ISSN (print): 2044-4753
ISSN (electronic): 2044-4761
Publisher: Royal Society of Chemistry
URL: https://doi.org/10.1039/C7CY02557B
DOI: 10.1039/C7CY02557B
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