Preparation of (E)-3-(3-((phenylamino)sulfonyl)phenyl)acrylic acid (6)
Malonic acid (145 g, 1.4 mol) was added in batches to a solution of 3-formyl-N-phenylbenzenesulfonamide 5 (240 g, 0.9 mol) and piperidine (18 mL, 0.2 mol) in pyridine (700 mL), then the mixture was stirred at 105–110 °C for 8.5 h. When TLC analysis indicated the disappearance of 5, the reaction mixture was cooled to ambient temperature and slowly poured into chilled 5% aqueous solution of sodium hydroxide (2.4 L) below 20 °C (pH: 9–10). The reaction mixture was washed with EA (1.2 L), and the separated organic layer was extracted with 5% aqueous solution of sodium hydroxide (600 mL). The aqueous layers were combined and cooled to 10–20 °C, then it was acidified slowly with 50% sulfuric acid (600 mL) below 20 °C (pH: 1–2). After the solution stirred for an additional 30 min at 15–20 °C, the solid obtained was collected by filtration and then washed with water (2.4 L) followed by n-hexane (1 L). The filter cake was dried in a vacuum oven at 50 °C to afforded colorless solid (E)-3-(3-((phenylamino)sulfonyl)phenyl)acrylic acid (244 g, 83%). mp 154–156 °C. 1H NMR (400 MHz, DMSO-d6) δ = 12.62 (bs, 1H), 10.32 (s, 1H), 8.01 (s, 1H), 7.94 (d, J = 7.8 Hz, 1H), 7.75 (d, J = 7.8 Hz, 1H), 7.63–7.56 (m, 2H), 7.24 (m, 2H), 7.11–7.01 (m, 3H), 6.55 (d, J = 16.0 Hz, 1H). MS (ESI):m/z = 326.0 [M+Na] +.
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KHAJURAHO, MADHYA PRADESH, INDIA
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