Iodine → Benzaldehyde, 4-hydroxy-3-iodo-5-methoxy-

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Reaction Conditions

Reaction Steps

Vanillin (28.4 g, 200 mmole (millimole)) was dissolved in 1N NaOH (200 ml) and warmed to 90° C. to avoid precipitation of sodium vanillate. A 2 molar aqueous solution of NaI3.NaI (105 ml, 210 mmole I2) plus 3.55 molar aqueous H2SO4 (5 ml) was added over 3 hours with stirring. The iodine color was discharged, and a pale tan stirrable precipitate formed. The solution was then cooled to room temperature, acidified to pH 2-3 with 20% aqueous H2SO4, and extracted with 10% methanol/90% chloroform. The organic phase was dried (MgSO4) and the solvent stripped to yield 53 g (99%) of 5-iodovanillin, more than 95% pure as analyzed by nuclear magnetic resonance spectroscopy (NMR).

Provenance & Evidence