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The starting material, p-methoxybenzenesulfinic acid was prepared from p-methoxybenzenesulfonyl chloride by a procedure similar to that described in the literature for m-carboxybenzenesulfinic acid (see Davis and Smiles) J. Chem. Soc. 97, 1274 (1910). The crude acid so obtained (30.7 g) was added to a solvent mixture consisting of 200 ml of water and 100 ml of dioxane. The pH was adjusted to ca 8.0 with dilute sodium hydroxide solution and 21.0 g of sodium bicarbonate was added. The mixture was stirred, heated to 60° C. and 20.0 g (0.1 mole) of p-methoxybenzenesulfonyl chloride was added slowly over a 2 hour period, while maintaining the reaction mixture at about 60° C. After stirring for an additional hour, 200 ml of cold water was added. The crude solid product was recovered by filtration. On drying, 8.4 g (24% crude yield) of product with m.p. 173°-174° C. was obtained; this product was crystallized from acetic acid, giving 7.5 g (22% yield) of white solid melting at 190°-191° C. with decomposition.

1. customThe crude acid so obtained (30.7 g)