N-heterocyclic carbene catalyzed α-redox reaction: catalytic synthesis of amides and carboxylic acids
Date
2011
Authors
Vora, Harit, author
Rovis, Tomislav, advisor
Williams, Robert, committee member
Wood, John, committee member
Chen, Eugene, committee member
McNeil, Michael, committee member
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Abstract
N-heterocyclic carbene catalyzed α-redox reaction has been utilized towards the catalytic synthesis of amides utilizing amines and substoichiometric quantities of an acyl transfer reagent in a waste reduced acylation process. The reaction is amenable to a plethora of amines and amine hydrochloride salts as nucleophiles. The reaction is applicable towards a variety α-reducible aldehydes as α,α-dichloro aldehydes, enals, epoxy and aziridnyl aldehydes all provide the respective amides in moderate to excellent yields with the latter in high diastereoselectivity. The asymmetric amidation reaction provides chiral amides in moderate enantioselectivity. Additionally, the N-heterocyclic carbene catalyzed α-redox reaction was also utilized for the synthesis of enantioenriched α-chloro and α-fluoro carboxylic acids. The reaction also provide for a mild installation of a deuterium from D2O furnishing enantioenriched isotopically labeled compounds. Investigations in to the mechanism have revealed that the carbene displays behavior of a phase transfer reagent by shuttling hydroxide from the aqueous phase to the organic phase. Additionally, it has been found that the turnover limiting step in this acylation process in the hydrolysis of the acyl azolium.
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Subject
synthesis
NHC catalysis
organic chemistry
asymmetric
catalysis