Preparation of 3‐hydroxyisoindolin‐1‐ones and o ‐acylbenzamides. A study of ring‐chain tautomerism

Abstract 3‐Hydroxyisoindolinones (ring form) as well as their chain tautomers, o ‐acylbenzamides, were prepared from the reactions of 3‐benzalphthalide 1 , 3‐halophthalides 3 , and o ‐acylbenzoic acids 6 or their esters 7 with amines 2 , and those of phthalimides 4 with Grignard reagents 5 . The characteristic spectroscopic properties of ring and chain forms are observed in the ir and 13 C‐nmr spectra. The significance of the spectroscopic results is discussed, as is the relationship between the structure of the products and the position of the ring‐chain equilibrium.