To a stirred solution of 2-amino-5-chloropyridine (573 mg, 4.51 mmol) in tetrahydrofuran (25 mL) at 0° C. under nitrogen was added methylmagnesium bromide (3.0 M in ether, 1.50 mL, 4.51 mmol) dropwise via a syringe. After stirring at 0° C. for 10 min, 2-(1,4-dioxa-8-azaspiro[4.5]decan-8-yl)-4H-3,1-benzoxazin-4-one (1.30 g, 4.51 mmol) was added. After stirring 15 h at room temperature, the solvent was removed in vacuo. The residue was partitioned between ethyl acetate and saturated aqueous sodium chloride and the layers separated. The organic phase was washed with water, dried (magnesium sulfate), filtered, and concentrated in vacuo to give, after recrystallization from EtOAc, 880 mg (47%) of the title compound.
