Table 1. Optimization of reaction conditions: the Rh-catalyzed cyclization of 1a with 2a ^a .

Entry	Solvent	Base	t/h	NMR yield b (%)
				3aa	4aa + 5aa
1	MeOH/H2O c	NaOAc	11	75	12
2	MeOH	NaOAc	21	80	14
3	DCE	NaOAc	21	58	17
4	DCM	NaOAc	21	65	21
5	Toluene	NaOAc	21	44	17
6 d	MeOH	NaOAc	14	80	16
7 e	MeOH	NaOAc	14	74	15
8	MeOH	KOAc	14	68	14
9	MeOH	CsOAc	14	69	14
10	MeOH	Na2CO3	14	69	14
11	MeOH	K2CO3	14	81 (72) f	14
12	MeOH	Cs2CO3	14	76	14
13	MeOH	K3PO4	11	73	13
14 g	MeOH	—	11	—	—
15 h	MeOH	K2CO3	13	75	14
16 i	MeOH	K2CO3	13	72	13
17 j	MeOH	K2CO3	13	18	7
18 g , k	MeOH	K2CO3	13	—	—

^aThe reaction was conducted with 1a (0.2 mmol), 2a (0.2 mmol), [Cp*RhCl₂]₂ (0.004 mmol), K₂CO₃ (0.06 mmol), MeOH (1.2 mL), and monitored by TLC.

^bDetermined by ¹H NMR using dibromomethane as internal standard.

^cThe ratio of MeOH/H₂O was 20/1 (1.2 mL/0.06 mL).

^dUnder N₂ atmosphere.

^eUnder N₂ atmosphere and 4 Å MS was added.

^fIsolated yield in parentheses.

^gRecovery of 1a was 98% with 2a disappeared.

^h10 mol% K₂CO₃ was added.

ⁱ50 mol% K₂CO₃ was added.

^j1 equiv. K₂CO₃ was added.

^kThe reaction was conducted in the absence of the Rh(iii) catalyst.