Table 1 Optimization of reaction conditions.

From: Dual Ni/photoredox-catalyzed asymmetric cross-coupling to access chiral benzylic boronic esters

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Entrya

Changes

Yield (%)

Ee (%)

1

No change

94 (86b)

93

2

Using Ni(cod)2

48

51

3

Using NiI2

43

90

4

L2 instead of L1

93

87

5

L3 instead of L1

19

91

6

L4 instead of L1

3

n.d.

7

[Ir(dFCF3ppy)dtbbpy]PF6 as PC

43

83

8

Ru(bpy)3Cl26H2O as PC

12

30

9

DME as solvent

45

94

10

DMA as solvent

42

82

11

No Et3N

<5

n.d.

12

Li2CO3 instead of TEA

36

85

13

No HEH

45

78

14

No 4CzIPN

7

90

15

No Ni or no light

0

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  1. aStandard conditions: 1a (1.6 equiv.), 2a (0.2 mmol), NiBr2·DME (10 mol%), L1 (12 mol%), 4CzIPN (1 mol%), HEH (2 equiv.), TEA (5 equiv.) DME/DMA (4 mL, v/v = 5/1), Blue LEDs (30 W), 18–25 oC, 8–10 h. Yields were determined by GC with ndodecane as an internal standard. The ee values were determined by HPLC.
  2. bIsolated yield was given in the parenthesis.
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