Table 1 Optimization of the reaction conditionsa

From: Design of C1-symmetric tridentate ligands for enantioselective dearomative [3 + 2] annulation of indoles with aminocyclopropanes

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Entry

Metal

L

x

Yieldb (%)

3a/4ac

drc

eed (%)

1

Cu(OTf)2

L1

10

23

83:17

7:1

81

2

Sc(OTf)3

L1

10

82

68:32

5:1

2

3

Yb(OTf)3

L1

10

Trace

   

4

Mg(OTf)2

L1

10

0

   

5

Fe(OTf)3

L1

10

75

70:30

7:1

53

6

Co(OTf)2

L1

10

79

79:21

8:1

69

7

Ni(OTf)2

L1

10

91

80:20

8:1

83

8

Zn(OTf)2

L1

10

65

80:20

8:1

73

9

Ni(OTf)2

L2

10

95

78:22

6:1

36

10

Ni(OTf)2

L3

10

93

80:20

9:1

89

11

Ni(OTf)2

L4

10

95

82:18

10:1

95

12

Ni(OTf)2

L5

10

92

81:19

10:1

92

13

Ni(OTf)2

L6

10

95

77:23

10:1

92

14

Ni(OTf)2

L7

10

90

76:24

6:1

−11

15

Ni(OTf)2

L8

10

38

75:25

8:1

15

16

Ni(OTf)2

L9

10

25

80:20

9:1

−2

17e

Ni(OTf)2

L4

10

98

82:18

10:1

98

18e

Ni(OTf)2

L4

5

98

82:18

10:1

98

19e

Ni(OTf)2

L4

2.5

74

80:20

10:1

95

20

Ni(OTf)2

tBu-Box

5

0

   

21

Ni(OTf)2

tBu-Pybox

5

0

   
  1. aReaction conditions: Metal/L (1:1.2, x mol%), 1a (0.1 mmol), 2a (0.2 mmol) in CH2Cl2 (2.0 mL) at 25 °C under N2 for 24 h.
  2. bThe total yield (3a + 4a) was determined by 1H NMR spectra of the crude product.
  3. cThe ratio of 3a/4a and dr value of 3a was determined by 1H NMR spectra of the crude product.
  4. dThe ee value of 3a was determined by chiral HPLC analysis.
  5. e2a (0.22 mmol).
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