Table 1. Optimization Condition for the Generation of β-Hydroxy-γ-Lactam 6a.

entrya	base	solvent	X–	yield of 6a (%)
1	NaH	THF	Br	10
2	t-BuOK	THF	Br	5
3	NaNH2	THF	Br	11
4	LDA	THF	Br	12
5	2,6-lutidine	THF	Br	5
6	KHMDS	THF	Br	10
7	DBU	THF	Br	18
8	DBU	DMF	Br	15
9	DBU	DMSO	Br	20
10	DBU	CH3CN	Br	25
11	DBU	dioxane	Br	17
12	DBU	CH3CN	OTf	20
13	DBU	CH3CN	BF4	45
14	DBU	CH3CN	BPh4	93b
15	DABCO	CH3CN	BPh4	87b
16	Et3N	CH3CN	BPh4	85b
17	piperidine	CH3CN	BPh4	90b

^aReaction conditions: 5 (0.20 mmol), base (0.20 mmol), and solvent (5.0 mL).

^bIsolated yield after silica gel column chromatography.