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The enol‐imine to keto‐enamine tautomerization involved in the formation of 3‐benzylamino‐5,5‐dimethylcyclohex‐2‐enone
Author(s) -
Kikta E. J.,
Bieron J. F.
Publication year - 1976
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270080407
Subject(s) - tautomer , enol , dimedone , keto–enol tautomerism , chemistry , imine , photochemistry , enone , medicinal chemistry , organic chemistry , catalysis
The formation of 3‐benzylamino‐5,5‐dimethylcyclohex‐2‐enone has been found to proceed through the initial formation of its enol‐imine tautomer. The enol‐imine has been isolated by a novel synthesis. It involves suspending dimedone in hexane for one hour at 67 °C with the amine in solution. Nuclear magnetic resonance spectroscopy has confirmed the tautomerization by observing the changing spectra as the enol‐imine tautomerizes to 3‐benzylamino‐5,5‐dimethylcyclohex‐2‐enone. The change in the nuclear magnetic resonance spectra is highlighted by a moving peak, which proceeds upfield with decreasing intensity as the tautomerization reaches completion. This moving peak involves chelated water formed in the initial condensation of dimedone and benzylamine. The chelated water acts as an active exchange agent which enhances the tautomerization rate. Similar results are obtained for the Schiff base derived from dimedone and aniline. This is the first isolation of the pure enol‐imine tautomeric form of 3‐benzylamino‐5,5‐dimethylcyclohex‐2‐enone. Under refrigeration the enol‐imine is found to be stable for over six months.