The invention discloses a method for preparing
alogliptin, a
medicine for treating
type II diabetes. The method comprises: 1) in the presence of
copper acetate and
triethylamine, 6-chloro-3-methyluracil and 2-cyano
Benzyl bromide is carried out
contact reaction in
acetonitrile, and after reaction finishes, reaction solution is poured into water, filters, washes with water, dries to obtain 6-chloro-1-(2-isocyanobenzyl)-3-methylpyrimidine-2, 4-(1H,3H)-dione; 2) 6-chloro-1-(2-isocyanobenzyl)-3-methylpyrimidine-2,4-(1H,3H)-dione, (R )‑3‑tert-butyloxycarbonylaminopiperidine and
potassium carbonate are mixed in DMF. After the reaction, add water, then extract with
dichloromethane and concentrate to obtain (R)‑tert-butyl‑1‑(3‑ (2‑isocyanobenzyl)‑1‑methyl‑2,6‑dioxo‑1,2,3,6‑tetrahydropyrimidin‑4‑yl)piperidin‑3‑ylcarbamate; 3 ) dissolving the
formate ester obtained in step 2) in
ethanol and reacting with
benzoic acid at 65-70°C, then cooling to -5-5°C for
crystallization, filtering and
drying to obtain
alogliptin. The invention has simple steps, high yield and faster reaction.