Olefin chlorination preparation process

The invention provides an olefin chlorination preparation process which comprises the following operation steps: adding a raw material 3-methyl-2-(7-oxo-3-p-tolyl-4-oxa-2, 6-diazabicyclo [3.2. 0]-hept-2-ene-6-yl)-3-dibenzoyl crotonate into a solvent to be dissolved, and adding a catalyst and a chlorination reagent to react; the preparation method comprises the following steps: adding 2-chloromethyl-2-(7-oxo-3-p-tolyl-4-oxa-2, 6-diazabicyclo [3.2. 0]-heptyl-2-ene-6-yl)-3-butenoic acid dibenzoyl ester into a reaction kettle, adding an anti-solvent, stirring, crystallizing, separating and drying to obtain the target product 3-chloromethyl-2-(7-oxo-3-p-tolyl-4-oxa-2, 6-diazabicyclo [3.2. 0]-heptyl-2-ene-6-yl)-3-butenoic acid dibenzoyl ester, the preparation method disclosed by the invention is simple to operate, chlorine is prevented from being used, the solvent can be recycled, reaction process conditions are mild, a high-purity and high-yield target product is finally obtained, and the preparation method is sui