Methanol → 5,6-O-benzylidene-L-ascorbic acid

Participants

Reaction Steps

L-Ascorbic acid (20 g), α,α-dimethoxytoluene (20 g) and a catalytic quantity (160 mg) of p-toluenesulfonic acid were dissolved in 60 ml of dimethylformamide. The solution was heated at 55°-60° C. for 4 hours. The reactor used for carrying out the reaction was equipped with a reflux-condenser connected to an aspirator, and the methanol formed during the reaction process produces was evaporated out of the reaction mixture. When the reaction was completed, the reaction solution was distilled under reduced pressure to remove the solvent. The resulting syrupy residue was washed with petroleum ether and water, each three times. Then, water and hexane were added to the washed syrup and the mixture was stirred to obtain a crystalline product of 5,6-O-benzylidene-L-ascorbic acid which was then filtrated off and dried to give 21.5 g of white colored crystals of 5,6-O-benzylidene-L-ascorbic acid (72% yield). The product thus obtained was nearly pure substance but was further purified by recrystallization from methanol or benzene. The final pure crystal showed mp. of 166°-168° C.

Provenance & Evidence