A Convenient Nucleophilic Iodinating Reagent

N,N-Dimethyl-N-(methylsulfanylmethylene)ammonium iodide (1) developed by Porter et al. is a novel nucleophilic iodinating reagent. It can convert primary and secondary alcohols to the corresponding iodo compounds. Though it is generally difficult to accomplish the iodination of allylic alcohols, 1 can replace them with the desired allyl iodides. In addition, primary alcohols react more rapidly than secondary alcohols, which allows selective iodination of primary hydroxy groups in primary-secondary diols. The similar iodinations using triphenylphosphine/iodinating reagents generate stoichiometric amounts of triphenylphosphine oxide, which often causes difficulty in product purification. In contrast, iodination using 1 has advantages such as easy work-up and product purification. Thus, 1 can be used as a convenient nucleophilic iodinating reagent.

Typical Procedure: Iodination of 2-(4-methylphenyl)ethanol
A solution of 2-(4-methylphenyl)ethanol (102 mg, 0.75 mmol) in toluene (3.5 mL) is heated to 85 °C. 1 (260 mg, 1.12 mmol) and imidazole (25 mg, 0.37 mmol) are added and the mixture is stirred at 85 °C for 90 min. After cooling to room temperature, the reaction mixture is concentrated in vacuo to afford the crude product. Purification by flash chromatography (SiO₂; petrol) affords 1-iodo-2-(4-methylphenyl)ethane as a colorless oil (170 mg, Y. 92%).