1,3-Propanediamine, N'-(ethylcarbonimidoyl)-N,N-dimethyl-, monohydrochloride → 2-(1,4-Dioxa-8-azaspiro[4.5]decan-8-yl)-4H-3,1-benzoxazin-4-one

To a stirring solution of 2-(1,4-dioxa-8-azaspiro[4.5]decan-8-ylcarbonyl)aminobenzoic acid (1.91 g, 6.25 mmol) in DMF (12 mL) was added 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (1.20 g, 6.25 mmol). After 30 min, the solvent was removed in vacuo and the residue was partitioned between ethyl acetate and water. The layers were separated and the organic phase was washed consecutively with 1 M citric acid, brine, satd aq sodium bicarbonate, and brine, then dried with MgSO4, filtered and concentrated in vacuo. The residue was then suspended in diethyl ether, sonicated, filtered and dried in vacuo to give 1.36 g of the title compound; which was used without further purification.