Table 1 Optimizations of reaction conditionsa.

From: Copper-catalyzed intermolecular formal (5 + 1) annulation of 1,5-diynes with 1,2,5-oxadiazoles

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Entry

Catalyst

Reaction conditions

Yield (%)b

1

CuOTf

DCE, 40 °C,6 h

37

2

Cu(MeCN)4BF4

DCE, 40 °C, 6 h

41

3

Cu(MeCN)4PF6

DCE, 40 °C, 6 h

53

4

Cu(MeCN)4PF6

DCM, 40 °C, 6 h

52

5

Cu(MeCN)4PF6

CHCl3, 40 °C, 10 h

30

6

Cu(MeCN)4PF6

PhMe, 40 °C, 10 h

28

7

Cu(MeCN)4PF6

PhCl, 40 °C, 9 h

47

8c

Cu(MeCN)4PF6

DCE, 40 °C, 6 h

38

9d

Cu(MeCN)4PF6

DCE, 40 °C, 6 h

52

10e

Cu(MeCN)4PF6

DCE, 40 °C, 4 h

68

11e

Cu(MeCN)4PF6

DCE, 40 °C, N2, 4 h

72

12e

Cu(MeCN)4PF6

DCE, 20 °C, N2, 12 h

71

13e

Cu(MeCN)4PF6

DCE, 60 °C, N2, 2 h

70

  1. aReaction conditions: 1a (0.05 mmol), 2a (2–10 equiv), catalyst (0.005 mmol), solvents (1 mL), 40–60 °C, 2–12 h, in vials.
  2. bMeasured by 1H NMR using 1,3,5-trimethoxybenzene as internal reference.
  3. c2 equiv of 2a was used.
  4. d10 equiv of 2a was used.
  5. e12 mol % of NaBArF4 was added.
  6. Ns = 4-nitrobenzenesulfonyl.
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