Synthesis and Tautomerism of Spiro-Pyrazolines
Sureshbabu Dadiboyena1, Edward J Valente2, Ashton T Hamme1
1Department of Chemistry & Chemistry, Jackson State University, Jackson, MS 39217 USA.
Abstract:
An experimental study on the synthesis, tautomerism and acid promoted structural changes of spiro-pyrazolines is described. The target was achieved through a [3+2]-dipolar cycloaddition of an alkene with nitrile imines generated in situ and was isolated in high yield. The synthesized cycloadduct displayed a tendency to exhibit an imine-enamine type of tautomerism as evidenced by X-ray crystal and NMR studies. Furthermore, addition of an acid resulted in the transformation of an imine tautomer to an enamine. The current report constitutes a first formal observation of this kind of tautomerism observed in spiro-indoline pyrazolines.
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