One-step liquid-phase heterogeneous synthesis of phenytoin using modified calcium oxide as a solid basic catalyst

A highly efficient heterogeneous method for the synthesis of phenytoin from benzil and urea has been established by using modified CaO as a solid basic catalyst. A relatively high yield of phenytoin was obtained (60.5 %) with a urea/benzil molar ratio of 2.5 at a reaction temper- ature of 40 C in the presence of commercial CaO. The yield of phenytoin was greatly enhanced to 90.8 % after treatment of commercial CaO with benzyl bromide. The results of Fourier transform infrared spectroscopy and thermogravimetry analysis implied that the modifier was chemically bonded onto the surface of CaO and almost no Ca(OH)2 was formed during the modification process. The effects of modification and reaction conditions on the yield as well as the possible mechanism were studied thoroughly.