Table 1.

Optimization of the reaction conditions.

Entry	Deviation from standard conditions	Yield (%)a	γ:β
1	None	78 (74)b	>20:1
2	NiBr2(DME), Ni(acac)2, Ni(COD)2	67–77	9:1–20:1
3	w/o ligand	24	>20:1
4	L7, instead of L8	66	10:1
5	L9, instead of L8	49	>20:1
6c	L6, instead of L8	34	>20:1
7	NiCl2(PPh3)2, instead of NiCl2(DME), L8	66	10:1
8	Ph2SiH2, instead of (EtO)2MeSiH	43	>20:1
9	THF only	72	12:1
10	DMA only	59	5.7:1
11	K2CO3, instead of Cs2CO3	22	1.8:1
12	Na2CO3, Li2CO3, no base	trace	-
13	w/o catalyst or silane	0	-

Reaction conditions: 1a (0.1 mmol), 2a (0.2 mmol), NiCl₂(DME) (10 mol%), L8 (30 mol%), base (0.2 mmol), hydride source (0.3 mmol), and solvent (0.5 mL) at 40 °C under Ar for 18 h.

DMA:N,N-dimethylacetamide.

^aYields and product isomer ratios (γ:β) were determined by ¹H NMR spectroscopy.

^b1 mmol scale.

^cLigand (15 mol%) was used.