The invention discloses a method for synthesizing watermelon
ketone. Under the protection of
nitrogen, inorganic or
organic base, PEG-400,
potassium iodide,
methanol, and 4-methyl pyrocatechol are added into a reactor and are heated to be between 65 and 70 DEG C, then 1,3-dichloroacetone is dripped into the mixture, and the mixture is subjected to
reflux reaction under
thermal insulation for 5 to 6 hours after the dripping is finished; a crude product is obtained through cooling and suction
filtration, and the
methanol is recovered;
ethyl acetate is added into the crude product, a saturated
saline solution is used to scrub to be neutral, and the
ethyl acetate is recovered; and the reduced pressure
distillation is performed, and a distillate is recrystallized by a mixed
solvent of the
methanol and n-
hexane to obtain a white crystalline
solid, namely the watermelon
ketone, wherein the
mass ratio of the 4-methyl pyrocatechol to the 1,3-dichloroacetone is 1 to 1, the
mass ratio of the inorganic or
organic base to the 4-methyl pyrocatechol is between 1 to 0.7 and 0.75, the
mass ratio of the
potassium iodide to the 4-methyl pyrocatechol is between 1 to 7.0 and 7.5, the
mass ratio of the PEG-400 to the 4-methyl pyrocatechol is between 1 to 20 and 30, and the
mass ratio of the methanol to the n-
hexane in the mixed
solvent is 1 to 2. The method adopts a one-pot method to synthesize a target product, and has the advantages of mild
reaction conditions, convenient operation, and high product yield.