aReaction conditions: alkyne 2 (0.50 mmol), B2Pin2 (0.50 mmol, 1.0 equiv), 1 (0.025 mmol, 5 mol %), toluene (0.5 mL), 23 °C. Numbers in parentheses are yields of isolated products obtained after purification by flash chromatography on silica gel. b0.25 mmol 2, 0.25 mmol 3, 10 mol % 1. c2.0 equiv 3. d4.0 equiv 3. e1.5 equiv 3. fThermal ellipsoids at 50% probability.