then stop heating cool to u2212 5 u00b0 c drop 200 ml tetrahydrofuran solution of 133 g 0 334 mol 1 0 eq n methoxyl n methyl 1 trityl 1h imidazole 4 formamide while the inner temperature is controlled to not exceed 25 u00b0 c after the dropping is complete continue to stir for 12 hrs at room temperature and then reaction ends add 50 g ammonium chloride which is dissolved in 150 ml water to quenching the reaction while controlling the inner temperature not exceeds 15 u00b0 c after dropping is complete add 500 ml dichloromethane stir for 1 hr at 10 u02dc 20 u00b0 c filter to remove insoluble substances the filtrate is separated into layers collect the organic phases extract the water phase by 3 u00d7 100 ml dichloromethane combine the organic phases and wash it by 2 u00d7 100 ml water concentrate the organic phase the residue is recrystallized in the solvents of 200 ml dichloromethane and 800 ml n hexane obtain 80 g 2 3 dimethyl phenyl 1 trityl 1h imidazole 4 ketone which is a light yellow solid with a yield of 54 and a purity of 84 hplc add 100 g 0 714 mol.