Dolbier HW Solutions 546 - -aminophenol is more...

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( c ) The amino group that is present in the starting material facilitates the introduction of the bromine substituents, and is then removed by reductive deamination. Hypophosphorous acid has also been used successfully in the reductive deamination step. ( d ) Reduction of the nitro group of the 1,3-dibromo-5-nitrobenzene prepared in the preceding part of this problem gives the desired product. The customary reducing agents used for the reduc- tion of nitroarenes would all be suitable. ( e ) The synthetic objective is This compound, known as acetaminophen and used as an analgesic to reduce fever and relieve minor pain, may be prepared from p -nitroaniline by way of p -nitrophenol. Any of the customary reducing agents suitable for converting aryl nitro groups to arylamines (Fe, HCl; Sn, HCl; H 2 , Ni) may be used. Acetylation of p -aminophenol may be carried out with acetyl chloride or acetic anhydride. The amino group of
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Unformatted text preview: -aminophenol is more nucle-ophilic than the hydroxyl group and is acetylated preferentially. 22.40 ( a ) Replacement of an amino substituent by a bromine is readily achieved by the Sandmeyer reaction. ( b ) This conversion demonstrates the replacement of an amino substituent by f uorine via the Schiemann reaction. 2. CuBr 1. NaNO 2 , HBr, H 2 O o-Anisidine OCH 3 NH 2 o-Bromoanisole (88 – 93%) OCH 3 Br 2. heat 1. NaNO 2 , H 2 O, H 2 SO 4 p-Nitroaniline p-Nitrophenol OH NO 2 NH 2 NO 2 1. reduce 2. acetylate p-Acetamidophenol OH HNCCH 3 O p-Acetamidophenol NHCCH 3 HO O Br Br NO 2 1,3-Dibromo-5-nitrobenzene [prepared from p-nitroaniline as in part ( c )] Br Br NH 2 3,5-Dibromoaniline (80%) H 2 , Ni NH 2 NO 2 p-Nitroaniline NH 2 Br Br NO 2 2,6-Dibromo-4-nitroaniline (95%) Br Br NO 2 1,3-Dibromo-5-nitrobenzene (70%) 1. NaNO 2 , H 2 O, H 1 2. ethanol Br 2 acetic acid 640 AMINES...
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