Table 1 Optimization of the Reaction Conditions[a]

From: Photo-induced intramolecular dearomative [5 + 4] cycloaddition of arenes for the construction of highly strained medium-sized-rings

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entry

PS

solvent

time (h)

yield of E-2a (%)[b], E/Z ratio[c]

1

I

DCM

48

0, /

2

II

DCM

24

0, /

3

III

DCM

24

84, 5.4/1

4

IV

DCM

24

86 (85[d]), 7.7/1

5

V

DCM

24

69, 2.8/1

6

VI

DCM

24

72, 2.9/1

7

IV

acetone

24

72, 5.4/1

8

IV

MeOH

24

0, /

9

IV

MeCN

24

82, 6.4/1

10

IV

dioxane

24

78, 6.2/1

11

IV

DMSO

24

71, 7.1/1

12

IV

EtOAc

24

76, 7.4/1

13[e]

/

DCM

36

0, /

14[f]

IV

DCM

36

0, /

  1. a Reaction conditions: 1a (0.1 mmol) and photosensitizer (PS, 1 mol%) in solvent (1 mL) were irradiated by blue LEDs (24 W, 455 nm) at room temperature under argon for a specified time.
  2. b 1H NMR yield of E-2a using C2H2Cl4 as an internal standard.
  3. c E/Z ratio determined by 1H NMR spectrum of the crude reaction mixture.
  4. d Isolated yield of E-2a.
  5. e In the absence of a PS.
  6. f In dark.
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