Retinol → Retinal

Participants

Reaction Conditions

Reaction Steps

57.2 g (0.2 mole) of crystalline all-trans vitamin A alcohol are dissolved in 1 liter of methylene chloride. The solution is then stirred at -20° C. to -35° C. in 10 minute intervals with a total of 90 g of nickel peroxide prepared in Example 4 in 5 portions. After the last portion has been introduced, the mixture is stirred for a further 15 minutes at -20° C. to -35° C., filtered off under suction and washed with a total of 1 liter of methylene chloride at -30° C. The residue collected on the filter has the spent nickel peroxide. The methylene chloride solution is subsequently concentrated to a volume of about 500 ml on a rotary evaporator. The residual solution is then treated with 500 ml of n-hexane, again evaporated to 500 ml, again treated with 500 ml of n-hexane and finally concentrated to a volume of 100 ml. The concentrate is cooled to 10° C., seeded with vitamin A aldehyde crystals and then left overnight at -20° C. to completely crystallise out. The crystals are then filtered off under suction, washed with 250 ml of pentane at -20° C. and dried in vacuo at 30° C. in a constant weight. There are obtained 49 g (86%) of vitamin A aldehyde with the expected melting point of 63.5°-65° C. and the UV value E11 = 1750 at 366 nm (hexane).

Provenance & Evidence