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Reagents and conditions: (a) Rh2(OAc)4 (5 mol%), toluene, 50 °C, 55 min; then Cu powder, 110 °C, 1.5 h, 85%. (b) ultraviolet light (λ=365 nm, Hg lamp), CHCl3, 22 °C, 8 h, 55%. (c) aq. HBr (48 wt%), AcOH, 120 °C, 10 h, 95%.
