Iodine → Di-gamma-linolenyl methanol

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Reaction Steps

Magnesium turnings (2.1 g, 87 mmol), 5 crystals of iodine and a stirbar were added to a 1000 mL round-bottom flask. The flask was flushed with nitrogen and a solution of γ-linolenyl bromide (Compound 6) (18.9 g, 57 mmol) in anhydrous diethyl ether (500 mL) added via cannula. The mixture turned cloudy and was refluxed overnight. The mixture was cooled to RT and ethyl formate (4.66 mL, 58 mmol) added dropwise. The suspension was stirred overnight, turning bright yellow. The R.M. was transferred to a 2000-mL sep funnel with ether (50 mL), and washed with 10% sulphuric acid (200 mL), water (2×200 mL) and brine (200 mL). The organic was dried over anhydrous MgSO4, filtered and concentrated. Crude yield was 14.5 g. TLC indicated that majority of product was the methyl formate, which was purified by column chromatography. The purified formate was transferred to a 1000 mL round bottom flask and EtOH (600 mL) and a stirbar added. With stirring, water (25 mL—forming ˜5% aqueous solution) was slowly added, followed by KOH (2.0 g, 35.7 mmol). After 1 hour, solution had turned pale yellow. TLC indicated reaction had gone to completion. The solution was concentrated by rotovap to 50% of its volume and then poured into 200 mL of 5% HCl. The aqueous phase was extracted with ether (3×200 mL). The ether fractions were combined and washed with water (3×200 mL), dried (MgSO4) and concentrated to yield 8.8 g of di-γ-linolenyl methanol (16.8 mmol, 58%).

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