Imidazole → 12-Iodo-1-dodecyne

Participants

Reaction Steps

Iodine (43.16 g, 170 mmol, 2.0 eq) was added to a suspension of distilled alcohol 61 (15.50 g, 85 mmol), imidazole (17.36 g, 255 mmol, 3.0 eq), and triphenylphosphine (66.90 g, 255 mmol, 3.0 eq) in dry toluene (425 mL, stored over molecular sieves). The reaction mixture was heated at reflux with vigorous stirring for 25 min, generating a yellow solution with a oily black precipitate. After colling to 25°, saturated aqueous sodium bicarbonate (200 mL) and iodine (23.73 g, 93.5 mmol, 1.1 eq) were added and the reaction was stirred vigorously for 1 h. Saturated aqueous Sodium sulfite (40 mL) was added, quenching the purple color. The reaction mixture was allowed to separate into two layers and the organic layer was washed with brine. The organic layer was dried over magnesium sulfate and concentrated. The residue was dissolved in dichloromethane (50 mL) and ether (200 mL) was added. After standing for 30 min, the resulting precipitate (triphenylphosphine oxide) was removed by filtration and washed with ether (100 mL). On further standing, the combined mother liquor and ether wash deposited a second crop of crystals which were removed as before. The combined mother liquors and ether washes were concentrated and dissolved in warm toluene (200 mL). This solution was placed on a silica gel column (500 g) and eluted with toluene (3 L) to afford 13.55 g (55%) of iodide 62 as a pale Yellow mobile liquid. This material was 96% one peak by GC.

Provenance & Evidence