Perchloric acid catalyzed acylations

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
John Lawrence McKenzie (Creator)
The University of North Carolina at Greensboro (UNCG )
Web Site:
Ben Edwards

Abstract: The object of this work was to explore the generality of acetic anhydride-perchloric acid catalyzed C-acylations, to determine experimental conditions which maximize C-acylation, and to further elucidate the mechanism by which the C-acylation occurs. The ability of acetic anhydride-perchloric acid systems to effect C-acylation of cyclohexanone, 3-methylcyclohexanone, and 4-methylcyclohexanone was demonstrated; the C-acylation yields are 36%, 40%, and 36% respectively. A reaction time of three hours with 1M acetic anhydride and 10-1M perchloric acid in a solvent of low dielectric constant and weak electron donating power such as chloroform gives maximum C-acylation. The molar ratio of 1:10:1 for ketone : acetic anhydride : perchloric acid was found best for C-acylation. Tar formation is a considerable problem and material balance studies indicate from 65% - 82% recovery of material. Several mechanistic possibilities are examined including: direct C-acylation of the enol form of the ketone, C-acylation of the enol acetate, and rearrangement of the enol acetate as possible mechanisms for the C-acylation of ketones in acetic anhydrideperchloric acid catalyzed systems. The direct C-acylation of the enol form of the ketone is found to be the mechanism most consistent with all the experimental data.

Additional Information

Language: English
Date: 1971
Perchloric acid

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