Triethylamine → 4-Oxazolecarboxylic acid, 5-(4-chlorophenyl)-, methyl ester

1.40 g (8.00 mmol) of 4-chlorobenzoyl chloride, 1.00 g (10.09 mmol) of methyl isocyanatoacetate and 5.9 ml (42.39 mmol) of triethylamine are dissolved in 15 ml of dry THF and stirred at RT for 48 h. The solvent is then removed on a rotary evaporator. The residue is taken up in 20 ml of ethyl acetate and washed once with 5 ml of water. The organic phase is dried over magnesium sulfate and the solvent is removed on a rotary evaporator. The residue is suspended in 10 ml of cyclohexane and filtered off. It is then recrystallized from about 10 ml of methanol. This gives needle-shaped crystals which are dried in a drying cabinet at 50° C. A further product fraction is obtained by reprecipitation after recrystallization.