3.2.9. Pinnick Oxidation of 9a

Aldehyde 9a (98 mg, 0.33 mmol) was dissolved in 7 mL of tert-butyl alcohol and 1.2 mL of 2-methyl-2-butene. A solution of sodium chlorite (85 mg, 0.94 mmol) and sodium dihydrogenphosphate dihydrate (95 mg, 0.61 mmol) in 1.5 mL of water was added dropwise over a 10 min period. The yellow reaction mixture was stirred at room temperature for 40 min. Volatile components were then removed under vacuum. The residue was dissolved in 30 mL of water and extracted with two 25 mL portions of MTBE. The combined organic layers were washed with brine, dried, and concentrated under reduced pressure. Purification by flash chromatography (H:MTBE, 10:1) afforded 69 mg of compound 10a [37] (0.22 mmol, 67%).

Compound 10a: ¹H NMR (600 MHz, CDCl₃) δ 7.31 (ta, J = 8,1 Hz, 1H), 7.29 (d, J = 8.1 Hz, 2H), 7.20 (d, J = 8.1 Hz, 1H), 7.13 (td, J = 6.8 Hz, 1H), 7.03 (t, J = 8.1 Hz, 1H), 7.01 (t, J = 7.4 Hz, 1H), 3.42 (s, 2H), 3.30 (s, 3H) (Figure S1h2). ¹³C NMR (151 MHz, CDCl₃) δ 175.94 (COOH), 148.14 (C), 143.39 (C), 135.62 (2C), 132.09 (CH), 129.76 (2CH), 128.05 (CH), 127.28 (CH), 124.47 (C), 121.90 (CH), 120.47 (CH), 40.47 (CH), 36.85 (CH₂) (Figure S1i2). HRMS TOF (ES+) m/z calculated for C₁₅H₁₄NO₂Cl₂ [M + H]⁺ 310.0402, found 310.0390.