Iodine → 4(2-Chloroallyl)benzaldehyde

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Reaction Steps

Dry Mg (0.58 g) under dry N2 in a flask is covered with THF (5 ml) and a crystal of I2 added. 5 ml of a solution of 4-bromobenzaldehyde ethylene acetal (5.0 g) in THF (25 ml) is added and kept until it becomes warm, when it is cooled to 15°, and the remainder of the acetal added over 15 min. then stirred for an additional 1 hour. A mixture of ground lithium chloride (0.35 g) and copper (I) chloride (0.70 g) dissolved in THF is prepared, treated with 1,2-dichloropropene (CH2Cl.CCl=CH2) (4.5 g) and cooled to -20°. The above Grignard solution (under moisture excluding conditions) is then added to this solution during 5 min, and allowed to warm to 20° with stirring for 16 hours. Saturated aqueous ammonium chloride is added and the organic layer evaporated under reduced pressure to a small residue, which is dissolved in THF (100 ml), cooled to -10°, treated with 3N HCl (50 ml), then stirred at 20° for 1 hour. The product is partitioned between ether and water, and the ether layer washed with NaHCO3, H2O NaCl, dried (MgSO4) and the residue chromatographed on florisil. The fraction eluted by 15% ether in petrol is collected and purified by preparative HPLC. Yield 0.55 g (13%) nD20 1.5571.

Provenance & Evidence