aReagents and conditions: alkyne 2 (0.50 mmol), PinB–BDan (0.50 mmol), 1 (5 mol %), THF, 50 °C, 36 h. Numbers in parentheses are yields of isolated products obtained after purification by flash chromatography on silica gel. Thermal ellipsoids in ORTEP diagram at 50% probability; hydrogen atoms except vinyl C–H omitted for clarity. Olefin geometry of products 6a, 6d, 6e, and 6g assigned by analogy to the solid-state structure.