title: Thermally induced sigmatropic isomerization of pseudosaccharyl allylic ether.
abstract: The thermally induced sigmatropic isomerization of the pseudosaccharyl allylic ether [3-(allyloxy)-1,2-benzisothiazole 1,1-dioxide; ABID] has been investigated by a multidisciplinary approach using temperature dependent infrared spectroscopy, differential scanning calorimetry, and polarized light thermomicroscopy, complemented by theoretical methods. Migration of the allylic system from O to N occurs in the melted ABID, and the thermally obtained 2-allyl-1,2-benzisothiazol-3(2H)-one 1,1-dioxide (ABIOD) starts to be produced at ca. 150 degrees C, in a process with an activation energy of approximately 92 kJ mol(-1). From kinetic data, a concerted [3,3'] sigmatropic mechanism is proposed. In the temperature range investigated, ABIOD was found to exhibit polymorphism. Cooling of the molten compound leads to the production of a metastable crystalline form, which upon annealing at room temperature might be transformed to the stable crystalline phase. ABID shows a single crystalline variety. Assignments were proposed for the infrared spectra of the observed neat condensed phases of the two compounds.
authors.affiliation: Department of Chemistry, University of Coimbra, P-3004-535 Coimbra, Portugal.
authors.forename: A
authors.initials: A
authors.lastname: Gómez-Zavaglia
authors.forename: A
authors.initials: A
authors.lastname: Kaczor
authors.forename: R
authors.initials: R
authors.lastname: Almeida
authors.forename: M L S
authors.initials: ML
authors.lastname: Cristiano
authors.forename: M E S
authors.initials: ME
authors.lastname: Eusébio
authors.forename: T M R
authors.initials: TM
authors.lastname: Maria
authors.forename: P
authors.initials: P
authors.lastname: Mobili
authors.forename: R
authors.initials: R
authors.lastname: Fausto