The thermal sigmatropic isomerization of pseudosaccharyl crotyl ether

Cabral L. I. L., Maria T. M. R., Martelo L., Eusebio M. E. S., Cristiano M. L. S., Fausto R.

TETRAHEDRON, vol.69, no.2, pp.810-815, 2013 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 69 Issue: 2
  • Publication Date: 2013
  • Doi Number: 10.1016/j.tet.2012.10.100
  • Journal Name: TETRAHEDRON
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Index Chemicus (IC)
  • Page Numbers: pp.810-815
  • Istanbul Kültür University Affiliated: Yes

Abstract

The thermally induced sigmatropic isomerization of the pseudosaccharyl crotyl ether, 3-(E)-but-2-enoxy)-1,2-benzisothiazole 1,1-dioxide (CBID), has been investigated by using temperature dependent infrared spectroscopy, differential scanning calorimetry (DSC), and polarized light thermomicroscopy. The reaction can take place in both melted and crystalline phases, affording the product resulting from the [3,3'] migration of the allylic system from O to N, 2-(E)-1-methylprop-2-en-1,2-benzisothiazol-3(2H)-one 1,1-dioxide (CBIOD). In the melt, the activation energy of the process was determined as being 49.1 +/- 5.3 kJ mol(-1), with k=(22.2 +/- 0.6)x10(4) s(-1) at 140 degrees C. In the solid state, at 110 degrees C, the rate constant drops by one order of magnitude [k=(1.46 +/- 0.07)x10(4) s(-1)]. The enthalpy of reaction, determined by DSC, is Delta H-rx=-27.0 +/- 0.8 kJ mol(-1). Assignments were proposed for the infrared spectra of the observed neat condensed phases of the two compounds. (c) 2012 Elsevier Ltd. All rights reserved.