Imidazole → Triphenylphosphine Oxide

Participants

Reaction Conditions

Reaction Steps

A 12-L, three-neck, round-bottom flask equipped with a mechanical stirrer, thermocouple, nitrogen bubbler, and an additional funnel, was charged with imidazole (204 g, 2.99 mol, 6.0 equivalents), triphenylphosphine (300 g, 1.14 mol, 2.3 equivalents), and methylene chloride (2.5 L). The resulting solution was cooled to −2° C. and to this was added iodine (290 g, 1.14 mol, 2.3 equivalents). The resulting mixture was allowed to stir for 15 minutes, and then a solution of (12) (274 g, 0.50 mol) in methylene chloride (1.3 L) was added slowly, over 35 minutes. The resulting orange mixture was allowed to warm to room temperature where it was stirred for three hours. The reaction mixture was filtered, and the filtrate was washed successively with 2% aqueous sodium sulfite solution (1×2 L), 0.1 N aqueous hydrochloric acid solution (1×1.5 L), and saturated aqueous sodium chloride solution (1×1.5 L). The organics were then dried over anhydrous magnesium sulfate and filtered. The solvent was removed in vacuo to afford a yellow residue which was dissolved in ether (4 L) producing a white precipitate (triphenylphosphine oxide). The solution was filtered and the filtrate was evaporated in vacuo to afford 320 g of (13) as a yellow oil contaminated with triphenylphosphine oxide. This material was used in the next step without purification.

Provenance & Evidence