Isothiazoles. Part VIII. Thermal rearrangement to α,β-unsaturated nitriles of cycloadducts from 3-diethylamino-4-(4-methoxyphenyl)-5-vinyl- isothiazole 1,1-dioxide with nitrile oxides and munchnones

3-Diethylamino-4-(4-methoxyphenyl)-5-vinyl-isothiazole 1,1-dioxide was reacted with nitrile oxides and munchnones affording the cycloadducts in good yields. The cycloaddition reaction occurred at the vinyl group exclusively. The cycloadducts undergo pyrolytic transformation into α,β-unsaturated nitriles through the isoxazole- or pyrrole-isothiazoline 1,1-dioxide intermediates.