Compound 22

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Compound data: 1H NMR

Compound data: 13C NMR

Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

To a 20 mL round-bottomed flask containing ammonium molybdate tetrahydrate (3.41 g, 2.76 mmol) was added aqueous H₂O₂ (35%, 24.3 mL, 276 mmol) at 0 °C. The resulting light yellow solution was stirred at room temperature for 15 min. A separate 250　mL　round-bottomed flask was charged with a solution of sulfide 21 in EtOH (70 mL) and cooled to 0 °C. The light yellow molybdate solution was added and the resulting suspension was stirred at room temperature. After 4 h, the vessel was cooled to 0 °C and the reaction mixture was quenched by careful addition of sat. Na₂SO₃ aq. (50 mL). The resulting mixture was then allowed to warm to room temperature. After partial evaporation of EtOH under reduced pressure, the mixture was extracted with EtOAc (30 mL × 3) and the combined organic layers were washed with brine (20 mL), dried over MgSO₄, filtered and concentrated under reduced pressure to provide sulfone 22 (3.84 g, 95%) as a white solid. The crude material was >95% pure by NMR and used as is in the subsequent step. R_f: 0.30 (25% EtOAc/ hexanes); Melting Point: 130–133 °C; Optical Rotation: [α]²²_D = −25 (c 0.20, CHCl₃); ¹H NMR (600 MHz, CDCl₃): δ 7.95 (d, J = 7.5 Hz, 2H), 7.62 (t, J = 7.5 Hz, 1H), 7.55 (t, J = 7.5 Hz, 2H), 6.70 (d, J = 5.5 Hz, 1H), 4.11 (d, J = 14.0 Hz, 1H), 3.18 (d, J = 14.0 Hz, 1H), 3.04 (ddq, J = 11.3, 6.8, 5.5 Hz, 1H), 2.36 (dt, J = 19.0, 5.5 Hz, 1H), 2.16 (ddt, J = 19.1, 11.3, 2.6 Hz, 1H), 1.81 (d, J = 2.0 Hz, 3H), 1.15 (d, J = 6.8 Hz, 1H), 0.96 (s, 3H); ¹³C NMR (151 MHz, CDCl₃): δ 200.2, 143.7, 141.8, 133.8, 133.5, 129.3, 127.9, 60.5, 49.4, 33.5, 31.2, 17.7, 16.8, 15.9; HRMS (ESI): Calc’d for C₁₆H₂₀O₃NaS [M+Na]⁺: 315.1025, found: 315.1020.