Table 1.

Optimization of the reaction conditions

Entry	Catalyst	Ligand	Additive	4aa (%)a,b
1	Ni(cod)2	PMe3	—	N.D.
2	Ni(cod)2	PPh3	—	N.D.
3	Ni(cod)2	PCy3	—	N.D.
4	Ni(cod)2	dmpe	—	N.D.
5	Ni(cod)2	dppe	—	N.D.
6	Ni(cod)2	dcype	—	78 (83:17)
7	NiCl2	dcype	—	Trace
8	NiBr2	dcype	—	Trace
9	NiBr2•glyme	dcype	—	Trace
10	Ni(acac)2	dcype	—	10 (78:22)
11	Ni(cod)2	dcype	NaI	91 (87)c (>95:5)
12d	Ni(cod)2	dcype	NaI	85 (>95:5)
13e	Ni(cod)2	dcype	NaI	71 (>95:5)
14f	Ni(cod)2	dcype	NaI	58 (>95:5)
15g	Ni(cod)2	dcype	NaI	78 (>95:5)
16h	Ni(cod)2	dcype	NaI	69 (>95:5)
17	Ni(cod)2	—	NaI	N.D.
18	—	dcype	NaI	N.D.

Reaction conditions: 3a (0.2 mmol), 1a (0.6 mmol), N₂H₄•H₂O (0.72 mmol), Ni(cod)₂ (10 mol%), ligand (20 mol% for monodentate, 10 mol% for bidentate), DIPEA (0.4 mmol), NaI (0.1 mmol), THF (1.0 mL), 100 °C, 12 h under N₂ unless otherwise noted

N.D. not detected

^aNMR yields were determined by ¹H NMR using mesitylene as an internal standard and based on 3a

^bThe E:Z ratio in parenthesis was determined by ¹H NMR analysis of the crude mixture

^cThe isolated yield in parenthesis

^d1a (0.4 mmol), N₂H₄•H₂O (0.48 mmol) instead

^e1a (0.3 mmol), N₂H₄•H₂O (0.36 mmol) instead

^f1a (0.2 mmol), N₂H₄•H₂O (0.24 mmol) instead

^gNi(cod)₂ (5 mol%), ligand (5 mol%) instead

^hWithout adding DIPEA