1) Solventless dibromination of 1,4-dimethoxybenzene

SyntheticPage 753
Published Aug 12, 2014

Procedure

1,4-dimethoxybenzene (0.56 g, 4.0 mmol) was placed in a mortar and pestle and sodium bromide (0.82 g, 8.0 mmol) was added. Oxone (2.45 g, 4.0 mmol) was added and the mixture was ground for approximately 15 min in the mortar until the reaction mixture had attained a uniform waxy texture. The solid was washed with water while grinding in the mortar, and collected on a fritted funnel. The product was recrystallized from 95% ethyl alcohol by transferring the solid to an Erlenmeyer flask and gradually heating with a heat gun while adding ethanol until the solid dissolved entirely. Slow cooling on the bench to room temperature followed by cooling in an ice bath gave white, needle-like crystals, which were collected by Buchner filtration and rinsed with ice-cold ethanol. (0.98g, 83% yield)

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2) Diiodination of 1,4-dimethoxybenzene in methyl alcohol

SyntheticPage 762
Published Sep 17, 2014

Procedure

Methanol (10 mL, see Author’s Note) was placed in a 50 mL round-bottom flask. 1,4-dimethoxybenzene (0.145 g, 1.0 mmol) was added, followed by iodine (0.26 g, 1.0 mmol) and 2 drops of 7.2M sulfuric acid. The flask was fitted with an open-top water-cooled condenser and brought to reflux by heating with a mineral oil bath on a hot plate. 30% aqueous hydrogen peroxide (2 mL, 2 mmol) were added in small portions over 5 min, and the mixture was refluxed for 4 h. The methanol was removed by rotary evaporation, and the solid residue taken up in approximately 10 mL of methylene chloride. This solution was shaken in a separatory funnel with aqueous sodium sulfite solution until the purple color of iodine was removed, dried over sodium sulfate and the solution gravity-filtered through a fluted paper. The solvent was removed by rotary evaporation to give 0.30 grams of a yellowish crystalline compound, 76% yield.

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