Nature Communications

Table 1 Optimization of reaction conditions^a

From: Enantioselective construction of C-B axially chiral alkenylborons by nickel-catalyzed radical relayed reductive coupling


Entry	[Ni]	L*	Additive	Solvent	Yield (%)^a	ee (%)^b
1	NiBr₂·DME	L1	none	THF	39	−30
2	NiBr₂·DME	L2	none	THF	42	71
3	NiBr₂·DME	L3	none	THF	33	71
4	NiBr₂·DME	L4	none	THF	48	86
5	NiBr₂·DME	L5	none	THF	39	68
6	NiBr₂·DME	L6	none	THF	trace	--
7	NiBr₂·DME	L7	none	THF	trace	--
8	NiBr₂·DME	L8	none	THF	trace	--
9^c	NiBr₂·DME	L4	none	2-MeTHF/DCE = 10/1	57	88
10^c,d	NiBr₂·DME	L4	none	2-MeTHF/DCE = 10/1	51	89
11^c,d	NiBr₂·DME	L4	MgCl₂	2-MeTHF/DCE = 10/1	72(70)^e	92
12^c,d	NiCl₂·DME	L4	MgCl₂	2-MeTHF/DCE = 10/1	51	87
13^c,d	NiBr₂	L4	MgCl₂	2-MeTHF/DCE = 10/1	18	88

^aReaction conditions: 1a (0.1 mmol, 1.0 equiv), 2a (1.3 equiv), 3a (3.0 equiv), NiBr₂·DME (10 mol%), L* (10 mol%), TDAE (2.1 equiv) in THF (1.0 mL) under argon at rt for 12 h. Yields were NMR yields. ^bThe enantioselectivity was determined by HPLC analysis. ^c1.0 mL of 2-MeTHF and 0.1 mL of DCE. ^d-5 ^oC for 24 h. ^eIsolated yields. L = ligand, 2-MeTHF = 2-methyltetrahydrofuran, DCE = 1,2-dichloroethane.

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