To produce protocatechuic aldehyde in high yield by chlorinating in the presence of a specific chlorine compound when producing the subject compound by way of piperonyl dichloride and dichloropiperonylidene dichloride from piperonal.
Piperonal of formula I is chlorinated with thionyl chloride in the presence of dimethylformamide to provide piperonyl dichloride of formula II and further the resultant compound of formula II is chlorinated by molecular chloride in the presence of a chlorine compound selected from phosphorus trichloride, phosphorus pentachloride and sulfuryl chloride to provide dichloropiperonylidene dichloride of formula III. Further the compound of formula III is hydrated to provide protocatechuic aldehyde of formula IV. Phosphorus trichloride is preferably used among the above chlorine compounds because of a low cost and an easy treatment. The quantity of the chlorine compound used in the reaction is about 0.05-15mol, especially about 0.1-1mol based on 1mol compound of formula I. The treatment of a phosphorus compound, which is a by-product, is simply performed and the produced protocatechuic aldehyde is easily purified by using this method.
KURODA NOBUYUKI
SHIRAI MASASHI
FURUYA TOSHIO
