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Reagents and conditions: (i) hydroxylamine-O-sulfonic acid, KHCO3, KI, H2O, 70 °C, 1.5 h, 94%; (ii) 3-butyne-2-one, KOH, CH2Cl2, rt, 16 h, 60%; (iii) DMF–DMA, 100 °C, 16 h, 91%; (iv) urea, sodium hydride, 140 °C, 10 min, 91%; (v) phosphorus(V)oxychloride, 110 °C, 3 h, 92%; (vi) thiourea, sodium methoxide, tert-butanol, 90 °C, 16 h, then iodomethane, 30 °C, 4 h, 27%; (vii) m-CPBA, CH2Cl2, rt, 16 h, 67%.
