First observation of Chapman rearrangement of a pseudosaccharyl ether in the solid state: the thermal isomerization of 3-(methoxy)-1,2-benzisothiazole 1,1-dioxide revisited

Abstract

3-(Methoxy)-1,2-benzisothiazole 1,1-dioxide, a pseudosaccharyl ether, was long ago known to undergo a thermal Chapman-like [1,3 0 ]-isomerization to the corresponding N-methyl pseudosaccharin at temperatures above its melting point (ca. 184 C) [Hettler H., Tetrahedron Lett. 1968, 15, 1793]. In the present study, it is shown that this rearrangement can also take place in the solid state, at temperatures as low as 150 C. This was the first observation of a Chapman-like [1,3 0 ]-isomerization in pseudosaccharyl ethers in the solid state. The study has been carried out by a multidisciplinary approach using temperature dependent infrared spectroscopy, differential scanning calorimetry (DSC), and polarized light thermomicroscopy, complemented by theoretical methods.

Conformational and structural analysis of 2-allyl-1,2-benzisothiazol-3(2H)-one 1,1-dioxide as probed by matrix-isolation spectroscopy and quantum chemical calculations

“…Therefore, the originally strong C A -O bond in the hydroxylic compound becomes weak, and the bond between the oxygen and the carbon of the heteroaromatic ring (C AR -O) becomes very strong [15]. In allyl-and alkylpseudosaccharyl ethers, the net result of the electronic changes is also important, in that it provides a molecular structure that lies close to a transition state structure, in which the originally strong C A -O bond in the ether becomes easily cleavable to give the ther-mally isomerised N-allyl or N-alkyl isomers, 2-allyl-or 2-alkyl-1,2-benzisothiazol-3(2H)-one 1,1-dioxides (benzisothiazolones), respectively, through Claisen-or Chapman-like rearrangements [16][17][18][19].…”

Synthesis and structure of novel benzisothiazole-tetrazolyl derivatives for potential application as nitrogen ligands

“…pseudo-saccharyl ethers, the net result of the electronic changes is also important, in that it provides a molecular structure that lies close to a transition state structure in which the originally strong C A -O bond in the ether becomes easily cleavable to give the thermally isomerised N-allyl-or N-alkyl-tetrazolones or benzisothiazolones, through Claisen-or Chapman-like rearrangements [6][7][8][9][10][11]. N-allyltetrazolones revealed to be important starting compounds for the easy preparation of new 2,3-dihydro-pyrimidinones [12,13].…”

Matrix-isolation FTIR, theoretical structural analysis and reactivity of amino-saccharins: N-(1,1-dioxo-1,2-benzisothiazol-3-yl)-N-methyl amine and -N,N-dimethyl amine

“…The saccharyl system, together with the oxygen from the original phenol or alcohol, represents an efficient nucleofuge in heterogeneous catalytic transfer hydrogenolysis [2][3][4] or cross-coupling with organometallic reagents [5]. The electron-withdrawing abilities of the benzisothiazolyl system are also in keeping with the easy thermally induced sigmatropic isomerisation of 3-allyloxy-and 3-alkoxy-derivatives of benzisothiazole to the corresponding N-allyl or N-alkyl isomers [6][7][8][9][10].…”

“…In recent studies on this family of compounds, we investigated the structure and spectroscopic properties of simple alkyloxy-and allyloxy-derivatives [specifically, 3-(methoxy)-1,2-benzisothiazole 1,1-dioxide and 3-(allyloxy)-1,2-benzisothiazole 1,1-dioxide] and the mechanisms involved in their thermal rearrangement to the corresponding N-alkyl or N-allyl isomers [9][10][11][12][13][14]. In those studies, the interpretation of the experimental data strongly relied on quantum chemical theoretical calculations, which had to be first duly calibrated in order to consider the specificities of the molecular systems under analysis.…”