Optimization of one-pot reaction conditions^a.

Entry	Equiv. of t-BuOLi	Yieldb (%)
1	1.3	—
2	1.5	—
3	2.0	60
4	2.5	83

^aReaction conditions: 8b (1 mmol), 9a (1.35 mmol), DIAD (1.5 mmol), PPh₃ (1.5 mmol), THF (8 mL), 0 °C–rt, 4 h; then t-BuOLi, THF, rt, 6 h.

^bIsolated yields.