Dibenzofuran → HCID 10737601, compound

Participants

Reaction Steps

To a solution of 4-trimethylsilyldibenzofuran (4) (7.93 g, 33.0 mmol) in dry diethyl ether (70 mL ) and TMEDA (7.97 mL, 52.8 mmol) cooled in an ice-water bath was slowly added n-BuLi (33.0 mL of 1.6 M solution in hexanes, 52.8 mmol) via a syringe. The resulting dark brown solution was stirred at room temperature for 5.5 hours. In a separate oven dried, 500 mL round bottom flask, I2 (19.2 g, 75.9 mmol) was dissolved in dry Et2O (70 mL) and cooled to -78° C. in an acetone-dry ice bath. The dibenzofuran anion was then slowly canulated into the stirring I2 solution. The resulting brown mixture was allowed to warm to room temperature while stirring overnight. The mixture was transferred to a cold (0° C.) solution of 20% NaHSO3 (~500 mL) and stirred vigorously. It was diluted with CH2Cl2 (~200 mL) and additional solid NaHSO3 was added until the mixture became pale yellow. Vigorous stirring was continued for 2.5 hours. The layers were separated and the aqueous layer was extracted with CH2Cl2 (2×100 mL). The combined organic layers were extracted with 20% NaHSO3 (2×150 mL), dried over magnesium sulfate and concentrated under reduced pressure to give a pale yellow solid. Dissolving the yellow solid in hexanes allowed separation of the compound from a brown, gummy, insoluble impurity. The hexane solution was decanted and concentrated under reduced pressure to give 12.5 g of compound (5). The crude material in hexanes (35 mL) was filtered through a silica gel column using hexanes (~300 mL ) as eluant. In this filtration only two 125 mL fractions were collected (t.l.c. rf=0.45 in hexanes). Since the second fraction appeared slightly yellowish, the two fractions were analyzed separately and combined later to give 8.57 g of a cream colored solid (75% based on 95% monosilylated dibenzofuran in the starting material). The melting points for the first and second fractions were 62-69° C. and 71-78° C., respectively. However, the two fractions were identical by 1H-NMR and HPLC. An analytical sample was obtained after purification by preparative C4 HPLC as a white solid: mp 74-77° C.; 1H NMR (CD3Cl) d 7.92 (dd, Jo=7.6, Jm=1.4, 1H, Ar H3), 7.90 (dd, Jo=7.6, Jm=1.5, 1H, Ar H7), 7.79 (dd, Jo=7.8, Jm=1.1, 1H, Ar H1), 7.56 (dd, Jo=7.2, Jm=1.4, 1H, Ar H9), 7.35 (t, Jo=7.6, 1H, Ar H8), 7.09 (t, Jo=7.7, 1H, Ar H2), 0.50 (s, 7H, --Si(CH3)3); 13C NMR (CD3Cl) d 156.33, 150.04, 135.47, 132.91, 124.39, 124.12, 123.50, 122.94, 122.88, 122.03, 120.47, -1.06; EIMS m/z 365.9877, M+ calcd for C15H15OISi 365.9939 and 350.9676, [M-CH3]+ calc 350.9704.

Provenance & Evidence