Chloral → Acetamide, 2-(hydroxyimino)-N-phenyl-

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Chloral hyrdate (17.40 g) is dissolved in water (256 mL) with sodium sulfate (108.75 g). The solution is warmed to 60° C. whereupon hydroxylamine hydrochloride (19.95 g) in water (124 mL) was added. In a separate flask a slurry of 2-iodo 5-aminotoluene (commercially available, Buttpark Ltd, U.K.) in water (139 mL) and CHCl (7.87 mL) was prepared at 80° C. The mixtures were combined and the reaction temperature increased to 95° C. for 20 min. then cooled to room temperature and then at 0° C. for 5 min. The solids were collected by filtration and washed with water (250 mL) and dried under vacuum to afford isonitrosoacetanilide 2.1 as a tan solid. Conc. H2SO4 (75 mL) was warmed to 50° C. and isonitrosoacetanilide 2.1 was added portionwise so that the temperature did not go above 70° C. After the addition the temperature was raised to 80° C. for 10 min. and then the mixture was allowed to cool to ambient temperature and poured onto ice water (10–12× volume). The isatin was filtered and washed with cold water (4×500 mL). The 1:1 isomeric mixture was taken up in 2N NaOH solution (316 mL) and stirred for 2 h then filtered. The filtrate was acidified to approx. pH 6 with acetic acid and refiltered to remove the undesired isatin isomer. The filtrate was acidifed to pH 1 with conc. HCl and filtered and the precipitate (desired isomer 2.7 g) was washed with water and dried by suction. Isatin 2 was converted to the corresponding aldehyde (3.1) as for isatin 1.1 above.

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