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Reagents and conditions: (a)285 polyphosphoric acid, 90–120 °C, 24 h; (b) (1) triisopropylsilylacetylene, n-BuLi, THF, 0 °C, 1 h then 147.2, rt, 6 h, (2) SnCl2·2H2O, HCl, rt, 3 h; (c)286 TfOH, MsOH, 140 °C, 4 h; (d) (1) triisopropylsilylacetylene, n-BuLi, Et2O, 0 °C, 1 h, then 147.6 or 147.9 in THF, rt, overnight, (2) SnCl2·2H2O, HCl, rt, 1 h.
