Scheme 4.
Reagents and conditions: (a) i. 1 or 2, SalPCl, Pyr, 1,4-dioxane, rt, 45 min; ii. tributyl ammonium pyrophosphate, tributylamine, DMF, rt, 45 min; iii. I2, H2O, Pyr, rt, 30 min.
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