CONICET | Buscador de Institutos y Recursos Humanos

Saccharin (1,2-benzisothiazol-3(2H)-one-1,1-dioxide) is a commonly known substance as it is the oldest artificial sweetener. Apart from the wide commercial applications of saccharin itself, its derivatives receive an increased attention as they show herbicidal, antimicrobial and antifungal activity or potential in enzymatic inhibition [1]. Substituted 1,2-benzisothiazole 1,1-dioxides (pseudosaccharins) are also important intermediates for reductive cleavage of the C-O bond in hydroxylic compounds, as their O-ethers provide efficient nucleofuges in catalyzed ipso-replacement reactions, such as heterogeneous transfer hydrogenolysis or cross-coupling with organometalic reagents. The increased reactivity of pseudosaccharyl ethers can be ascribed to structural changes induced by the electron withdrawing saccharyl system, resulting in a considerable increase in length of the original O-CA bond (A= benzyl, allyl, naphthyl or aryl) [2]. In this work, the pseudosaccharyl ether 3-(methoxy)-1,2-benzisothiazole 1,1-dioxide (3MBID) has been studied structurally by means of matrix isolation spectroscopy in argon, krypton and xenon matrices. The interpretation of the experimental results was supported by extensive DFT calculations performed at the B3LYP/6311++G(3df,3pd) level of theory. According to the results obtained, 3MBID belongs to the Cs symmetry point group. It has 54 fundamental vibrations, all active in the infrared. 3MBID has only one rotational axis (about the N8=C9-O15-C17 dihedral angle) that can give rise to conformers. However, the two conformers predicted by the calculationsdue differ very much in energy (ca. 47 kJ mol-1). Because of that, the population of the less stable conformer is exceedingly small and only the conformational ground state has practical significance. In consonance with the theoretical predictions, only the most stable form of 3MBID could be isolated in the rare gas matrices.

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