Yield:26518-76-3 91%

Reaction Conditions:

with aluminum (III) chloride in dichloromethane; for 5.16 h;Cooling with ice;Reflux;

Steps:

21.1 Step 1:

Step 1: (0399) 2H-1,4-benzoxazin-3(4H)-one 21-a (500 mg, 3.356 mmol) was suspended in dichloromethane (8 ml). Anhydrous aluminum chloride (895 mg, 6.712 mmol) was added portionwise under ice bath, then chloroacetyl chloride (330 ul, 4.363 mmol) was added slowly dropwise. The reaction mixture was stirred at room temperature for 10 minutes, then at reflux for 5 hours. The reaction was quenched with water, concentrated. The residue was added with ice water (10 ml), 4N hydrochloric acid (5 ml) and stirred for 2 hours at room temperature, then filtered, the filter cake was washed with ice water twice, dried to give 21-b as a pale yellow solid (690 mg, yield: 91%).

References:

US2017/158680,2017,A1 Location in patent:Paragraph 0397; 0398; 0399