Method of preparing Alogliptin

The invention relates to Alogliptin, benzoate thereof and a preparation method of an intermediate of the Alogliptin. The method comprises the following steps: alkylating 6-chlorouracil by using 2-(bromomethyl)benzonitrile on the basis of a tetrahydrofuran solvent and the catalysis of alkali to generate N-benzyluracil derivatives, and further alkylating by using methanol through a Mitsunobu reaction to obtain 1,3-disubstituted uracil (intermediate). The method does not need a NaH risk agent and highly toxic agent methyl iodide in the prior art, and is safe and environment-friendly.