Studies on isoindoline derivatives and related compounds. I Synthesis and reduction of 1,3‐dicarboethoxymethyleneisoindoline

The reaction of iminoether III with benzyl cyanoacetate gave ethyl 1‐(α‐cyanocarbobenzyl‐oxymethylene)isoindoline‐3‐acetate (V) in a 26% yield. Decarboxylation of ethyl 1‐(α‐cyanocarboxymethylene)isoindoline‐3‐acetate (VI), obtained by hydrogenolysis of V, gave a mixture of 1‐carboethoxymethyleneisoindoline‐3‐acetonitrile (VII) as major component and 1‐carboethoxymethylene‐3‐cyanomethyleneisoindoline (VIII) as minor component, which were reconvertible into each other. On the other hand, decarboxylation of VI was successfully carried out to give VII as a single product under a nitrogen atmosphere. Ethanolysis and autoxidation of VII gave crystalline diethyl 1,3‐dicarboethoxymethyleneisoindoline (XIII). Catalytic hydrogenation of of XIII over platinum oxide gave diethyl isoindoline‐ cis ‐1,3‐diacetate (XIV) in a yield of 92%. The uv spectra of these 1,3‐disubstituted isoindoline derivatives are summarized in Table I.