20348-21-4

16867-03-1

600-00-0

20348-21-4

Step - (i): Synthesis of 2,2-dimethyl-2H-pyrido[3,2-B][1,4]oxazin-3(4H)-one (18.1) 2-Amino-3-hydroxypyridine (5 g, 45.45 mmol) was dissolved in acetone (50 mL) at 20-35 °C and stirred to form a solution. Subsequently K2CO3 (25.09g, 181.81mmol) was added followed by dropwise addition of ethyl 2-bromo-2-methylpropionate (13.29g, 68.18mmol). The reaction mixture was stirred at 70 °C for 16 hours. After completion of the reaction, the mixture was cooled to 20-35 °C and diluted with ice water. The resulting solid was collected by filtration and washed with water to afford the target compound as a white solid (5g, 97% yield). 1H NMR (400MHz, DMSO-d6): [specific NMR data should be added here].