title: Synthesis and Tautomerism of Spiro-Pyrazolines.
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 generatedin situand 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.
authors.affiliation: Department of Chemistry & Chemistry, Jackson State University, Jackson, MS 39217 USA.
authors.forename: Sureshbabu
authors.initials: S
authors.lastname: Dadiboyena
authors.affiliation: Department of Chemistry, University of Portland, Portland OR 97203 USA.
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Valente
authors.affiliation: Department of Chemistry & Chemistry, Jackson State University, Jackson, MS 39217 USA.
authors.forename: Ashton T
authors.initials: AT
authors.lastname: Hamme
keywords: 1,3-Dipolar Cycloaddition; Heterocycles; Indolines; Regioselectivity; Spiro-isoxazolines; Spiro-pyrazolines; Tautomerism