2,4-Dichloro-5-(chlorosulphonyl)benzoic acid → 4-Methyl-5-methylsulfonylanthranilic acid

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Reaction Steps

This product is prepared by replacing the 2,4-dichloro-5-chlorosulfonylbenzoic acid employed in Example 1, Step A, by an equimolecular proportion of 4-methyl-5-chlorosulfonylanthranilic acid and then following substantially the same procedure described in Example 1, Steps A and B, there is obtained 4-methyl-5-methylsulfonylanthranilic acid employed in the following step without purification. The compound thus obtained is combined with excess furfural and heated on a water bath at about 80° C. The water formed during the reaction is removed by azeotropic distillation with the excess furfural at about 15 mm. Hg. pressure over a one hour period. The 2-furfurylideneamino-4-methyl-5-methylsulfonylbenzoic acid formed is stirred while cooling in acetic acid while a mixture of trimethylamine-borane complex in acetic acid is added over a 10 minute period. The reaction mixture then is heated on the steam bath for 5-10 minutes, then quenched in ice water to give 2-furfurylamino-4-methyl-5-methylsulfonylbenzoic acid.

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