Reaction development^a.

Entry	Variation from the standard conditions	Yieldb [%]
1	None	77 (72)c
2	CoCp*(CO)I2, [IrCp*Cl2]2, Cu(CH3CN)4PF6 instead of [RhCp*Cl2]2	0
3	RhCp*(OAc)2·H2O instead of [RhCp*Cl2]2	59
4	[Ru(p-cymene)Cl2]2 instead of [RhCp*Cl2]2	63
5	With 1.0 equiv. of NaOAC	58
6	With 1.0 equiv. of PivOH	40
7	36 h instead of 18 h	76
8	12 h instead of 18 h	74
9	120 °C instead of 100 °C	74
10	80 °C instead of 100 °C	65
11	1.5 equiv. of 2a, 36 h	73
12	3 mol% [RhCp*Cl2]2	60
13	Without [RhCp*Cl2]2	0
14	Under air	63

^aReaction conditions: 1a (0.1 mmol), 2a (0.2 mmol), [RhCp*Cl₂]₂ (6 mol%), HFIP (1.0 mL), 100 °C, Ar, 18 h.

^bDetermined by ¹H NMR analysis of the crude reaction mixture.

^cIsolated yield. HFIP: hexafluoroisopropanol.