Table 1 Condition screening of photolysis

From: Ti(Oi-Pr)4-promoted photoenolization Diels–Alder reaction to construct polycyclic rings and its synthetic applications

Entry

λ max (nm)

Acid (3.0 equiv.)

Solventb

Time (h)

Conversion (%)c

Yield (9 + 10, %)c

Yield (11, %)c

Ratio (9/10)c

1

366

None

Toluene

2.0

100

ND

Trace

–

2

366

TFA

Toluene

3.5

82

ND

5.4

–

3

366

PTSA.H2O

Toluene

3.5

87

ND

1.3

–

4

366

TMSOTf

Toluene

2.0

99

ND

ND

–

5

366

BF3 .Et2O

Toluene

2.0

60

ND

ND

–

6

366

Sc(OTf)3

Toluene

2.0

76

ND

ND

–

7

366

Yb(OTf)3

Toluene

2.0

98

16

0.8

2.2:1

8

366

Ti(Oi-Pr)4

Toluene

0.5

100

56

1.6

14.3:1

9

300

Ti(Oi-Pr)4

Toluene

0.75

96

55

3.2

4.8:1

10

254

Ti(Oi-Pr)4

Toluene

1.5

98

19

1.5

3.4:1

11

366

Ti(Oi-Pr)4

Toluene (dry)

0.5

100

60

2.9

20:1

12

366

Ti(Oi-Pr)4

Chlorobenzene

0.5

100

61

3.4

12.5:1

13

366

Ti(Oi-Pr)4

CH2Cl2

1.5

100

36

5.6

1:2.1

14

366

Ti(Oi-Pr)4

CH3CN

2.0

94

22

8.0

6.2:1

15

366

Ti(Oi-Pr)4

EtOH

1.5

30

ND

Trace

–

16

366

Ti(Oi-Pr)4

Cyclohexane

0.5

100

67

4.8

4.8:1

17

366

Ti(Oi-Pr)4

Et2O (dry)

0.5

100

61

4.0

16.7:1

18

366

Ti(Oi-Pr)4

Dioxane (dry)

0.5

100

67

3.1

20:1

19d

366

Ti(Oi-Pr)4

Dioxane (dry)

0.5

100

72e

–

50:1

20

None

Ti(Oi-Pr)4

Dioxane (dry)

72.0

14

ND

ND

–

  1. ND not detected
  2. aConditions: aldehyde (0.1 mmol), unsaturated ketone (0.6 mmol), conc.=0.02 mol/L
  3. bAll the photoreactions were conducted in degassed solvent
  4. cConversions, ratios and yields were determined by 1H NMR analysis of crude mixtures using CH2Br2 as an internal standard, unless noted
  5. dRecrystallized aldehyde (0.5 mmol) was used
  6. eIsolated yield
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