To a solution of (2-chloro-5-methoxy-phenyl)-acetic acid (1 g) in tetrahydrofuran (20 ml) were added N,N-dimethylformamide (2 drops) and oxalylchloride (1.03 g). The mixture was stirred overnight at room temperature. The solvent was evaporated; toluene was added and again evaporated. The residue was dried under high vacuum to give the crude acid chloride. To a cooled solution (ice bath) of 4-methyl-2H-1,4-benzoxazin-3(4H)-one (830 mg) in 1,2-dichloroethane (5 ml) was added AlCl3 (1.99 g). The mixture was stirred for 10 min and a solution of the acid chloride in 1,2-dichloroethane (5 ml) was added dropwise. The mixture was stirred at 0° C. for 4.5 h. The mixture was poured into ice water and hydrochloric acid and extracted with dichloromethane. The organic phase was dried (MgSO4), filtered and concentrated. The product was purified by chromatography (SiO2, cyclohexane/EtOAc 1:0=>0:1) to give the title compound (1.6 g) as an off-white solid. MS (m/e)=346.1 [M+H+].
