Bromine → 2-imino-8-trifluoromethoxy-2H,4H-thiazolo[5,4,3-ij]quinolin-6-one

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Reaction Steps

The procedure is carried out as in Example 1, but starting with 2.2 g of bromine in 10 ml of acetic acid, 3.09 g of potassium thiocyanate and 3.2 g of 6-trifluoromethoxy-2,3-dihydro-(1H)-quinolin-4-one in 35 ml of acetic acid. The organic phase is extracted with 170 ml of an approximately 0.1 N aqueous hydrochloric acid solution. The aqueous hydrochloric phase is alkalinized with 4 ml of a 10 N sodium hydroxide solution and extracted with three times 100 ml of ethyl acetate. The organic extracts are combined, washed with 100 ml of distilled water, dried over magnesium sulphate and concentrated to dryness under reduced pressure (2 kPa) at 40° C. The crude io product obtained is chromatographed on silica gel, eluting with a mixture of ethyl acetate and petroleum ether (80-20 by volume). The yellow solid isolated (0.3 g) is washed with a cold solution of petroleum ether and of isopropyl ether (60-40 by volume), and is then dried under reduced pressure (70 Pa) at 40° C. 0.25 g of 2-imino-8-trifluoromethoxy-2H,4H-thiazolo-[5,4,3-ij]quinolin-6-one is thus obtained in the form of a yellow powder melting at 192° C. [Analysis C11H7F3N2O2S, % calculated C: 45.84, H: 2.45, F: 19.77, N: 9.72, O: 11.1, S: 11.12, % found C: 45.5, H: 2.1, F: 19.4, N: 9.3, S: 11.1].

Provenance & Evidence