Scheme 2.
Reagents and conditions: (a) NBS/H2SO4/H2O, 92%; (b) (CH3)2SO4/K2CO3/acetone, 95%; (c) SeO2/dioxane, 80 °C, 71%; (d) SeO2/dioxane, 80 °C, 75%; (e) (CH3)2SO4/K2CO3/acetone; (f) acetyl chloride, AlCl3/CS2, 76%; (g) SeO2/dioxane, 80 °C, 74%.
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