Synthesis method of 4,6-dichloropyrimidine with 4,6-dihydroxypyrimidine serving as midbody

The invention provides a synthesis method of 4,6-dichloropyrimidine with 4,6-dihydroxypyrimidine serving as a midbody. The synthesis method mainly comprises the following steps: adding sodium methylate, dimethyl malonate and formamide into a reaction kettle, fully stirring, then increasing the system temperature, performing heat preservation reaction to remove byproducts, slowly adding sodium methylate drop by drop again, keeping the temperature for half an hour after completion of adding, and performing desolventizing; adding water when the solution is hot, and stirring to cool the solution to realize crystallization; performing centrifugal spin-drying to obtain centrifugal filtrate and crystallized solids, intensively refining and recycling the filtrate, and directly esterifying solid sodium salt; transferring for alkaline hydrolysis, and filtering to obtain a 4,6-dihydroxy pyridine solution; adding trichloromethane and a pyridine catalyst; stirring, slowly feeding phosgene and controlling the reaction temperature; decompressing to distill redundant trichloromethane, and continuously performing suction filtration, concentration and crystallization to obtain white needle-shaped products. The preparation method disclosed by the invention is simple; production of a large amount of wastewater due to multiple acid modulations is avoided; the product yield is high, and the synthesis method is suitable for industrial production.