Screening of reaction conditions^a.

Entry	Variation from the standard conditions	3cb	1b	4b	Fluorenoneb
1	None	99	0	0	0
2	With no use of base	0	100	0	0
3	KOH instead of t-BuOK	85	10	0	0
4	t-BuONa instead of t-BuOK	∼5	71	21	0
5	NaOH instead of t-BuOK	Trace	72	25	0
6	CsOH·H2O instead of t-BuOK	26	54	∼5	0
7	K2CO3 instead of t-BuOK	0	100	0	0
8	100 °C instead of 120 °C	10	48	40	0
9	1,4-Dioxane instead of toluene	92	∼5	0	0
10	THF instead of toluene	Trace	88	10	0
11	0.5 mmol (100 mol%) t-BuOK	90	∼5	∼5	Trace
12	0.75 mmol (150 mol%) t-BuOK	60	∼5	∼5	28
13	1.0 mmol (200 mol%) t-BuOK	50	∼5	0	40
14c	0.125 mmol (25 mol%) t-BuOK	99	0	0	0
15d	0.05 mmol (10 mol%) t-BuOK	99	0	0	0

^aThe standard conditions: fluorene (0.5 mmol), 4-methoxybenzyl alcohol (1.5 mmol), base (0.25 mmol, 50 mol% relative to fluorene), solvent (4 mL), 120 °C, in N₂, 3 h.

^bThe crude product examined quantitatively by ¹H NMR and qualitatively by TLC; NMR yields determined by ¹H NMR analysis using 1,3,5-trimethoxybenzene as an internal standard.

^cReaction time: 24 h.

^dReaction time: 48 h.