piperidones 2-(2,6-dioxopiperidin-3-yl)-1H-isoindole-1,3(2H)-dione 2-(2,6-dioxopiperidin-3-yl)-1H-isoindole-1,3(2H)-dione A dicarboximide that is isoindole-1,3(2<em>H</em>)-dione in which the hydrogen attached to the nitrogen is substituted by a 2,6-dioxopiperidin-3-yl group. 2-(2,6-dioxopiperidin-3-yl)-1H-isoindole-1,3(2H)-dione phthalimides