Compound 10a

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Compound data: 1H NMR

Compound data: 13C NMR

Compound data: Crystallographic data

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

In an oven-dried round-bottom flask, a suspension of dione 14 (0.219 g, 0.493 mmol, 1 equiv.) in dry THF (25 ml) was cooled to −78 °C under a N₂ atmosphere. In a separate oven-dried round bottom flask, 2-bromomesitylene (0.6 mL, 3.94 mmol, 8 equiv.) was dissolved in dry THF (25 ml), cooled to −78 °C under a N₂ atmosphere, and n-BuLi (2.5 M in hexanes, 1.47 ml, 3.69 mmol, 7.5 equiv.) was added dropwise. After stirring the mixture at −78 °C for 1 hour, the aryl lithiate was transferred via cannula to the flask containing the dione. This reaction mixture was slowly warmed to room temperature overnight with stirring. The reaction was then quenched with a saturated aq. NH₄Cl solution and extracted with Et₂O (3×). The combined organic layer was washed with brine, dried (MgSO₄) and concentrated in vacuo. The resulting crude oil was passed through a silica plug eluting with hexanes, followed by a CH₂Cl₂ wash, to provide the desired diol that was carried onto the reductive dearomatization step without further purification. In a single-neck round-bottom flask the crude diol (0.05 g, 0.073 mmol, 1 equiv.) and anhydrous SnCl₂ (33 mg, 0.175 mmol, 4 equiv.) were dissolved in dry degassed toluene (15 ml). Trifluoroacetic acid (catalytic) was added and this mixture was then vigorously stirred. The reaction was monitored via TLC (9:1 hexanes/CH₂Cl₂). After 3 hours, the mixture was poured over a silica plug and washed with hexanes. Switching to 1:1 hexanes/CH₂Cl₂ eluted the product. The solvent was evaporated and the solid was washed with cold MeCN to remove trace impurities. The remaining solid was redissolved in CHCl₃ and MeCN was layered over the solution to furnish IIDBT 10a as deep purple crystals (0.199 g, 62% from 14); ¹H NMR (500 MHz, CDCl₃, 25 °C) δ (ppm) 7.62 (d, J = 8.0 Hz, 2H), 7.17 (s, 2H), 7.16 (t, J = 8.1 Hz, 2H), 7.08 (t, J = 7.6 Hz, 2H), 7.03 (s, 4H), 6.91 (d, J = 7.7 Hz, 2H), 6.84 (s, 2H), 2.41 (s, 6H), 2.20 (s, 12H); ¹³C NMR (151 MHz, CDCl₃, 25 °C) δ (ppm) 148.22, 147.56, 145.45, 141.61, 141.07, 140.60, 139.95, 135.80, 134.75, 133.71, 133.29, 133.09, 131.43, 130.27, 128.60, 128.29, 126.89, 125.00, 32.81, 23.59; HRMS (ES⁺) (m/z), calculated for C₄₆H₃₅S₂ (M+H)⁺ 651.2180, found 651.2184.