Iodine → N-(4-carboxyphenyl)-5-phenyl-4-isothiazolin-3-one

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Compound of Formula (I) in which R1, R2, R4 and R5 =H, Ar1 =Ar2 =phenyl and R3 =4-CO2H A mixture of 1.449 g (0.005 mole) N-(4-carboxyphenyl)-3-mercapto-3-phenylpropenamide (A. Yokoyama, K. Ashida and H. Tanaka, Chem. Pharm. Bull. 12 (6), 690-5 (1964)), 3 mL (excess) triethylamine, 100 mL water and 100 mL ethanol was stirred at room temperature. Added, portionwise, was 1.269 g (0.005 mole) iodine and the mixture stirred at room temperature for 3 hrs. The solution was filtered and the filtrate was acidified to pH 1 with concentrated hydrochloric acid. The resulting solid was filtered and recrystallized twice from ethanol/water to provide 0.350 g (1.180 mmol, 23%) N-(4-carboxyphenyl)-5-phenyl-4-isothiazolin-3-one as a white powder, mp=238°-240° C. NMR (CDCl3 /TMS): 6.6 (S, 1H), 7.5-7.6 (m, 5H), 7.9 (d, 2H), 8.2 (d, 2H). IR (Nujol): 3481, 1698, 1619. High resolution mass spectrum: Calculated; 298.053790. Measured; 298.053472. Anal. calcd. for C16H11NO3S: C 64.65, H 3.70, N 4.71, S 10.77; Found C 64.52, H 3.64, N 4.59, S 10.75.

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