The Thermally Induced Sigmatropic Isomerization of Pseudosaccharyl Allylic Ether

A. GÓMEZ-ZAVAGLIA, A. KACZOR, R. ALMEIDA, M.L. CRISTIANO, M. E. EUSÉBIO, T. MARIA, P. MOBILI, R. FAUSTO.

JOURNAL OF PHYSICAL CHEMISTRY A

American Chemical Society

Lugar: New York.; Año: 2009 vol. 113 p. 3517 - 3522

1089-5639

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 (DSC) 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 ºC, in a process with an activation energy of ~92 kJ mol-1. In the temperature range investigated, ABIOD was found to exhibit polymorphism, having a metastable crystalline form (melting point: ca. 50 ºC) and stable crystalline phase (melting point: ca. 80 ºC). ABID shows a single crystalline variety. Assignments were proposed for the infrared spectra of the observed neat condensed phases of the two compounds.