Table 1 Optimization of reaction conditions for asymmetric Büchner reaction of N-propargyl ynamide 1a

From: Asymmetric Büchner reaction and arene cyclopropanation via copper-catalyzed controllable cyclization of diynes

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Entry

L

Reaction conditions

Yield (%)a

Ee (%)b

1

L1

DCM, 35 °C, 0.5 h

86

49

2

L2

DCM, 35 °C, 0.5 h

83

55

3

L3

DCM, 35 °C, 0.5 h

71

<5

4

L4

DCM, 35 °C, 0.5 h

79

11

5

L5

DCM, 35 °C, 0.5 h

90

42

6

L6

DCM, 35 °C, 0.5 h

94

79

7

L7

DCM, 35 °C, 0.5 h

93

41

8

L8

DCM, 35 °C, 0.5 h

86

51

9

L9

DCM, 35 °C, 0.5 h

95

81

10

L9

DCE, 35 °C, 0.5 h

94

84

11

L9

toluene, 35 °C, 0.5 h

94

85

12

L9

THF, 35 °C, 0.5 h

95

70

13

L9

toluene, 0 °C, 8 h

93

87

14

L9

toluene, −20 °C, 40 h

95

96

  1. Reaction conditions: 1a (0.05 mmol), Cu(MeCN)4PF6 (0.005 mmol), L (0.006 mmol), NaBArF4 (0.006 mmol), solvent (1 mL), in Schlenk tubes.
  2. aMeasured by 1H NMR using diethyl phthalate as internal standard.
  3. bDetermined by HPLC analysis. Ms = methanesulfonyl, Mes = mesityl, NaBArF4 = sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, DCM = dichloromethane, DCE = 1,2-dichloroethane, THF = tetrahydrofuran.
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