Compound 4

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Compound data: NMR

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

Recrystallized N-bromosuccinimide (28.6 g, 161 mmol, 2.0 equiv) was added in one portion to a vigorously stirring solution of 4-methylbenzenethiol (10 g, 80.4 mmol, 1.0 equiv) in DCM (100 mL) and methanol (100 mL) at 0 °C (ice/water) before warming to ambient temperature and stirring for 1 h. The mixture was poured into NaHCO₃ (saturated aqueous solution, 200 mL) at 0 °C (ice/water) and shaken until discoloration. The organic phase was collected, and the aqueous phase was extracted with DCM (2× 100 mL). The combined organic phases were dried (MgSO₄) and concentrated under reduced pressure. The residue was purified by flash column chromatography (SiO₂; 67:30:3 pentane:DCM:EtOAc) to yield the sulfinate 4 (10.5 g, 76 %) as a colorless oil. Note: if the product is coloured (occasionally a bright yellow or pink color), it should be dissolved in DCM and passed through a plug of activated charcoal. TLC: R_f = 0.24 (67:30:3 pentane:DCM:EtOAc). ¹H NMR (400 MHz, CDCl₃) δ 7.60 – 7.57 (m, 2H, 2× ArH), 7.35 – 7.33 (m, 2H, 2× ArH), 3.46 (s, 3H, OCH₃), 2.43 (s, 3H, ArCH₃) ppm. ¹³C NMR (101 MHz, CDCl₃) δ 143.0 (ArC), 141.1 (ArC), 129.9 (ArCH), 125.5 (ArCH), 49.5 (OCH₃), 21.6 (ArCH₃) ppm.