Table 1.

Optimization of reaction conditions^a

Entry	Ni Cat.	Ligand	Reductant	Solvent	Yield of 4 (%)	Recovery of 1a (%)
1	NiBr2•DME	L1	Zn	DMA	0	77
2	NiBr2•DME	L2	Zn	DMA	0	87
3	NiBr2•DME	L3	Zn	DMA	6	73
4	NiBr2•DME	L4	Zn	DMA	30	52
5	NiBr2•DME	L5	Zn	DMA	0	97
6	NiBr2•DME	L6	Zn	DMA	14	79
7	Ni(acac)2	L4	Zn	DMA	15	83
8	Ni(OTf)2	L4	Zn	DMA	25	55
9	Ni(COD)2	L4	Zn	DMA	12	54
10	Ni(PPh3)2Cl2	L4	Zn	DMA	35	47
11	Ni(PPh3)2Cl2	L4	Zn	DMSO	0	70
12	Ni(PPh3)2Cl2	L4	Zn	CH3CN	0	94
13	Ni(PPh3)2Cl2	L4	Zn	EtOAc	0	88
14b	Ni(PPh3)2Cl2	L4	Zn	DMA	60	21
15b,c	Ni(PPh3)2Cl2	L4	Zn	DMA	55	63
16b	Ni(PPh3)2Cl2	L4	Mn	DMA	4	64
17b	Ni(PPh3)2Cl2	L4	TDAE	DMA	trace	72
18b,d	Ni(PPh3)2Cl2	L4	Zn	DMA	79 (73e, 55f)	0

DME dimethyl ether, DMA N,N-dimethylacetamide, acac acetylacetonate, OTf triflate, COD 1,5-cyclooctadiene, DMSO dimethyl sulfoxide, EtOAc ethyl acetate, TDAE tetrakis(dimethylamino)ethylene.

^aReaction conditions: 1a (0.2 mmol), 2a (0.3 mmol), 3a (0.6 mmol), Ni catalyst (10 mol%), ligand (12 mol%), reductant (0.6 mmol), solvent (1 mL), 25 °C, 24 h, N₂ atmosphere.

^bLigand (20 mol%) was used.

^c1a (0.3 mmol), 2a (0.2 mmol) were used.

^dThe reaction run at 35 °C for 36 h.

^eThe isolated yield was shown in parentheses on 0.4 mmol scale.

^f(3-iodopropyl)benzene as the substrate.