Cheap synthetic method of watermelon ketone

The invention discloses a cheap synthetic method of watermelon ketone. The cheap synthetic method comprises the following specific operation process: refluxing sodium hydroxide and 4-methyl catechol in a methanol solution for 0.5-1 hour, and performing reduced-pressure rotary evaporation on the alcohol solution to obtain 4-methyl catechol disodium salt; adding DMF into the 4-methyl catechol disodium salt, adding a small amount of sodium hydride, then slowly adding 1, 3-dichloroacetone into the reaction system, reacting for 0.5-1 hour at the room temperature, then performing reflux reaction, pouring the system into ice water after TLC detection shows that reaction is completed, extracting for 3-5 times by using dichloromethane, eluting a dichloromethane layer by using saturated salt water for 3-5 times, drying an organic layer by using anhydrous sodium sulfate, performing reduced-pressure rotary evaporation, and performing column separation on residues to obtain the watermelon ketone. The cheap synthetic method is lower in reaction temperature, simple in synthetic process and easy to operate; and by the cheap synthetic method, a small amount of sodium hydride is used, the watermelon ketone is high in yield and high in purity, by-products are fewer, and the production cost is low.