Synthesis of novel tricyclic isoindole derivatives

Novel 3-methylene-2,5-dioxo-3H,9bH-oxazolo[2,3-a]isoindoles were prepared from the thermolysis of (3R,9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindole-3-carboxylic acids in acetic anhydride. The structure of 3-methylene-2,5-dioxo-3H,9bH-oxazolo[2,3-a]isoindole 6a was determined by X-ray crystallography. (C) 2003 Elsevier Ltd. All rights reserved.