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0 °C

According to Scheme 2 Step 2: A mixture of 6-bromo-1,2,4-triazine-3,5(2H,4H)-dione 2(A) (943 mg, 4.91 mmol), CH2Cl2 (40 mL), triphenylphosphine (1.76 g, 6.69 mmol), (2,2-difluorobenzo[d][1,3]dioxol-5-yl)methanol (840 mg, 4.46 mmol) was stirred at 0° C. under nitrogen atmosphere. Di-tertbutyl azodicarboxylate (2.05 g, 8.93 mmol) was added portionwise and the mixture was stirred for 16 hours at room temperature. 200 mL of water were added and the aqueous layer was extracted thrice with 200 mL of DCM. The organic layers were combined and were successively dried over MgSO4, filtered and concentrated under reduce pressure to afford a brown solid. The crude solid was purified by flash chromatography with silica gel (Merck Flashmart prepacked column SiO2) using AcOEt/cyclohexane 3/7 as eluant to afford 6-bromo-4-((2,2-difluorobenzo[d][1,3]dioxol-5-yl)methyl)-1,2,4-triazine-3,5(2H,4H)-dione 5(A) (330 mg, 20%) as a white solid.

1. stirringthe mixture was stirred for 16 hours at room temperature
2. extractionthe aqueous layer was extracted thrice with 200 mL of DCM
3. dry with materialwere successively dried over MgSO4
4. filtrationfiltered
5. concentrationconcentrated
6. customto afford a brown solid
7. customThe crude solid was purified by flash chromatography with silica gel (Merck Flashmart prepacked column SiO2)