Isobutyronitrile (IV) was prepared from isobutyric acid (I) through isobutyryl chloride (II) and isobutyramide (III), and was led to isopropyl ketone by the Grignard reaction with ethyl iodide or bromide. Isonitrosation of (V) yielded 2-isonitroso-4-methylpentan-3-one (VI) which was reduced and acetylated to 2-N-acetylamino-4-methylpentan-3-one (VII) and followed by hydrolysis with hydrochloric acid to 2-amino-4-methylpentan-3-one (VIII), obtained as the hydrochloride. (VIII) was condensed with ethyl oxalylacetate by the method of Corwin et al. to afford 2-methyl-3-isopropyl-4-ethoxycarbonyl-5-carboxypyrrole (IX) which was hydrolyzed with potassium hydroxide and decarboxylated to (XII). This substance formed a picrate of 2 moles of (XII) and 1 mole of picric acid, as in the case of 2, 3-dimethylpyrrole.
