Benzene (20 ml.) was added to a solution of phosgene 2.5 g.) in benzene (11.4 ml.). To the solution was dropwise added a solution of diethyl 2-hydroxyiminomalonate (4.73 g.) and N,N-dimethylaniline (3.03 g.) in benzene (30 ml.) over 40 minutes at 5° C in nitrogen stream. The mixture was stirred for 1 hour at the same temperature and overnight at room temperature. To the resultant mixture containing diethyl 2-chlorocarbonyloxyiminomalonate was dropwise added a solution of 4-methoxybenzyl alcohol (3.11 g.) and pyridine (4.04 ml.) in benzene (30 ml.) over 40 minutes at 5° C. The mixture was stirred for 2 hours at the same temperature, for 3 hours at room temperature and allowed to stand overnight. Cold water (100 ml.) was added to the reaction mixture to dissolve an insoluble material and cooled 1N-hydrochloric acid (20 ml.) was added thereto, after which the mixture was shaken. The organic layer was in turn washed 3 times with 1N hydrochloric acid (20 ml.), 3 times with a 5% sodium carbonate aqueous solution (20 ml.) and a sodium chloride aqueous solution, and then dried over magnesium sulfate. After drying the solvent was distilled off to give diethyl 2-(4-methoxybenzyloxycarbonyloxyimino)malonate (6.89 g.), pale brown oil, which was solidified on standing at ambient temperature.
