We have described an efficient synthesis of quino[2,3-b][1,5]benzoxazepine α-aminophosphonate derivatives by the nucleophilic addition of triethyl phosphite to substituted quino[2,3-b][1,5]benzoxazepines promoted by easily available, inexpensive and mild catalyst KAl(S$O_4)_2{cdot}12H_2$O(alum). The reactions proceed smoothly at room temperature under solvent-free reaction conditions and providing high yield of product in very short reaction time.