Carbon tetrabromide → HCID 53304915, compound

Participants

Reaction Conditions

Reaction Steps

Anhydrous dichloromethane (530 mL) was added to a 1 L of dry round-bottomed flask and cooled to −22° C. Triphenylphosphine (19.5 g, 74 mmol) was added and then added the β-lactol (2b, 23.5 g, 53 mmol). To that solution, carbon tetrabromide (26.3 g, 79.5 mmol, solid) was added portionwise over 5 min. at −22° C. The reaction was slowly warmed up to room temperature and once reaction was complete, the solution was passed through a short pad of silica gel (148 g in a 600 mL of fritted disc Buchner funnel) to remove any brown color polar impurities. The colorless filtrate was concentrated to dryness under reduced pressure and the solid residue was dissolved in ethyl ether (170 mL). Hexanes (50 mL) was added slowly until a precipitate started to form. The product was collected as a light yellow solid via filtration and dried (0.2 mm Hg, 25° C., 17 h) to afford 21.23 g, (79%) with an anomeric ratio of α/β>65:1. The product was contaminated with 3-4% of triphenylphosphine oxide which had no effect on the next reaction step. 1H NMR (CDCl3): δ 8.05 (m, 2H, arom.), 7.95 (m, 2H, arom.), 7.47-7.40 (m, 4H, arom.), 6.33 (s, 1H, C1-H), 5.22 (m, 1H, C3-H), 4.84 (m, 1H, C4-H), 4.76 (m, 1H, C5-Ha), 4.62 (m, 1H, C5-Hb), 1.69 (d, 3H, CH3, J=21.6 Hz).

Provenance & Evidence