Table 1 Different catalytic systems for synthesizing C₅ carboxylic acids from THF, CO₂, and H₂.


Entry	Catalyst precursor	Promoter	Solvent	Yield of (2a + 2a’) [%]^a
1^b	IrI₄	LiI	AcOH	70
2	IrI₄	LiI	AcOH	44
3	–	LiI	AcOH	0
4	RhI₃	LiI	AcOH	<1
5	CoCl₂	LiI	AcOH	<1
6	FeI₂	LiI	AcOH	0
7	RuI₃	LiI	AcOH	<1
8	PdCl₂	LiI	AcOH	<1
9	PtCl₂	LiI	AcOH	<1
10	IrI₄	–	AcOH	0
11	IrI₄	NaI	AcOH	2
12	IrI₄	KI	AcOH	<1
13	IrI₄	MgI₂	AcOH	0
14	IrI₄	ZnI₂	AcOH	0
15	IrI₄	LiCl	AcOH	<1
16	IrI₄	LiBr	AcOH	<1
17	IrI₄	I₂	AcOH	10
18	IrI₄	CH₃I	AcOH	<1
19	IrI₄	LiI	hexanoic acid	37
20	IrI₄	LiI	DMF	0
21	IrI₄	LiI	Toluene	0
22	IrI₄	LiI	DMSO	0
23	IrI₄	LiI	H₂O	0
24	IrI₄	LiI	1-ethyl-3-methylimidazolium acetate	0

Reaction conditions: 20 μmol catalyst precursor, 2 mmol promoter, 0.6 mL solvent, 2.45 mmol THF, 5 MPa CO₂ (68 mmol) and 2 MPa H₂ (at room temperature), 170 °C, 8 h
^aYield is based on THF feedstock (100 × moles of 2a and 2a’ per mole of THF feedstock)
^bThe reaction time was 16 h and the 2a accounted for 58% of total products (2a + 2a’)

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