Sodium Dithionite → 6,7-Dichlorothieno[3,4-b](1,5]benzoxazepine-10(9H)-one

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Reaction Steps

A 20.87 g. portion of the preceding product (prepared as described above) is stirred in 210 ml. of acetone and 210 ml. of water, then 87.0 g. of sodium dithionite is added portionwise with stirring at room temperature as described in J. Chem. Soc., 4727 (1956). The resulting colorless mixture is heated on a steam bath for 1/2 hour, then is cooled and extracted four times with ether. The ether layer is washed 3 times with brine, then is dried over anhydrous sodium sulfate and evaporated to provide yellow crystals. This material is recrystallized from methylene chloride/hexane to yield 3.63 g. of 2-amino-4,5-dichlorophenol as buff colored crystals. A 4.81 g. amount of this product (prepared as described) is dissolved in 35 ml. of methylene chloride then a 3.51 ml. portion of triethylamine is added and the mixture is stirred. To this is added dropwise with stirring 48 ml. of a solution of 9.90 g. of 4-ethoxy-3-thiophenecarbonyl chloride (prepared as described in Example 1 ) dissolved in 100 ml. of methylene chloride. The mixture is allowed to stir overnight then the precipitate is collected, air dried, triturated with water, collected and dried to yield 4.95 g. of 4',5'-dichloro-4-ethoxy-2'-hydroxy-3-thiophenecarboxanilide.

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