Nickel-Catalyzed Synthesis of Dialkyl Ketones from the Coupling of N-Alkyl Pyridinium Salts with Activated Carboxylic Acids |
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Authors: | Dr Jiang Wang Megan E Hoerrner Prof Mary P Watson Prof Daniel J Weix |
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Institution: | 1. Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706 USA;2. Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716 USA |
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Abstract: | While ketones are among the most versatile functional groups, their synthesis remains reliant upon reactive and low-abundance starting materials. In contrast, amide formation is the most-used bond-construction method in medicinal chemistry because the chemistry is reliable and draws upon large and diverse substrate pools. A new method for the synthesis of ketones is presented here that draws from the same substrates used for amide bond synthesis: amines and carboxylic acids. A nickel terpyridine catalyst couples N-alkyl pyridinium salts with in situ formed carboxylic acid fluorides or 2-pyridyl esters under reducing conditions (Mn metal). The reaction has a broad scope, as demonstrated by the synthesis of 35 different ketones bearing a wide variety of functional groups with an average yield of 60±16 %. This approach is capable of coupling diverse substrates, including pharmaceutical intermediates, to rapidly form complex ketones. |
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Keywords: | acyl fluorides cross-coupling ketone synthesis nickel pyridinium Salts |
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