Optimization^a.

Entry	Deviation from the above	Temp., time	5aa (%)
1	NiBr2·diglyme, THF	45 °C, 4 h	60c
2	NiBr2·diglyme, THF	60 °C, 4 h	92
3	NiCl2, THF	60 °C, 4 h	29d
4	Ni(acac)2, THF	60 °C, 4 h	66
5	NiBr2bpy, THF	60 °C, 4 h	21
6	THF	60 °C, 4 h	86
7	20 mol% of CuI or CuCN	60 °C, 4 h	2
8	bpy instead of dtbpy, THF	60 °C, 4 h	70d
9	TMEDA instead of dtbpy, THF	60 °C, 4 h	28d
10	dppe instead of dtbpy, THF	60 °C, 4 h	10
11	Toluene	60 °C, 4 h	38
12	None	60 °C, 4 h	95
13	None	rt, 12 h	90
14	5 mol% Ni(OAc)2·4H2O	rt, 12 h	94 (86)f
15	2 mol% Ni(OAc)2·4H2O	rt, 12 h	52
16	Ni(COD)2 (1.5 eq. 3a), THF	rt, 12 h	95
17	Without Ni(OAc)2·4H2O	rt, 12 h	2
18	Silylzinc from PhMe2SiLi	rt, 12 h	23
19	1 eq. LiCl additive	rt, 12 h	42
20	4.2 mmol of 2a	rt, 12 h	(80)

^aReaction conditions: 0.39 mmol of 3a, 0.234 mmol of PhMe₂SiZnI·TMEDA 2a (0.66 M in toluene), 0.0195 mmol of Ni(OAc)₂·4H₂O and dtbpy, 0.17 M (overall concentration). Isolated acid-chloride 4a was used in entries 1–7 and 17–19; in situ acid-chloride 4a was used in entries 8–16 and 20.

^bYield determined by ¹H NMR using 1,3,5-trimethoxy benzene as an internal standard.

^c1.3 eq. of PhMe₂SiZnI.

^dIncomplete reaction; unreacted starting material was observed in the crude NMR.

^e1.0 eq. of PhMe₂SiZnI was used.

^fReactions were repeated at least 10 times throughout the project. DME: 1,2-dimethoxy ethane, yield in parentheses is isolated yield.